There are a number of nice compact, all in one, PA mixer/amplifiers. One of the Fender's comes to mind. Mackie & Beringer also have similar affordable systems albeit they don't necessarily all fold together as a single unit like the Fender. So the Fender is one of the quickest to set up & tear down. And like most of these, still offer a stereo record output for your computer.

AT, DPA & a whole lot of others today offer a quality wearable over the ear microphone which are best suited & paired with a wireless belt pack transmitter. Of course you can still go wired. Your MP3 player isn't necessarily practical to make wireless. That can still be done with yet another wireless belt pack transmitter fitted with a specialized cord with compatible connectors in lew of the microphone. Of course that would be mono but still perfectly fine. Basically, what we're talking about is a wireless belt pack guitar transmitter where your MP3 player is the guitar.

Now all less than $600, that generally is not a realistic figure for all the wireless stuff to be included. It's barely adequate just for the PA. That means, you may need to make some serious compromises such as being all wired. You might also need to just purchase a Radio Shaft tie tack microphone. You would take that tie tack microphone tape and/or glue a thick piece of ROMEX solid, not stranded, electrical wire, to the microphone. That way, you could affix that bendable copper wire (with the installation still on it, choice of black or white) mounted from a pair of glasses, back near your ear to put it into close proximity to your mouth, utilizing a couple of inches of that solid core copper wire. Particularly since you are not putting your mouth where your money is. So you have to become ingenious and creative and custom modify things to make up for your loss of budget. That's what real audio guys do when you absolutely positively have to work within a fixed budget.

I've stripped wire with my teeth and custom-made devices to use for NBC television, Washington DC when emergency situations arose and the particular piece of equipment needed wasn't in the house. So you go find what you can find and start to tear it apart, combining it with other things you have torn apart and voilà! You are on the air in minutes time.

After posting this, I realized I neglected to say, Radio Shaft has inexpensive awful wireless microphones. They also have cheap ass PA amplifiers and crappy available speakers. With the above mentioned tie-tack microphone, you may be able to accomplish this within your budget. But check with your music store nevertheless.

Custom kludger
Mx. Remy Ann David

Anything of quality and (importantly) reliability is going to set you back more than $600.

I have people hire my Yamaha StagePas 300 or the 500 for this sort of work. The 300 can give cut-out problems when run in a big room, so I generally advise the 500 for an audience above 50-75 listeners. The 500 has a compressor/limiter on the first two mic channels. The hirers usually also take a selection of A-T wireless headsets and lav mics for the speakers at the event and hand-held radio mics for passing round the audience members at question time, plus grunt MP3 and CD players for walk-up and interval music. These all plug into the mixer/amplifier box of the StagePas. You can take a -10dBV feed out to an MP3 recorder if you want a audio recording of the event.

This sort of rig is quite portable. The mixer/amplifier stows away in the rear of one of the speakers and the cables in the rear of the other. You need carry boxes for the mics, CD players, etc, and you also have the speaker stands as separate items, but it all can be up and running in less than 10 minutes from arrival at a venue once you know what you are doing.

Just what the doctor ordered:

[[url=http://[/URL]="http://www.sweetwat…"]Fender Audio Passport 500 Pro | Sweetwater.com[/]="http://www.sweetwat…"]Fender Audio Passport 500 Pro | Sweetwater.com[/]

(This entire post is assuming that you will use this system frequently for your work, and will need this for long-term service. Otherwise, if it's just for very infrequent things just a few times a year, or not long-term at all...you may be better off just renting a small system for (probably) $100-250 a pop.)

About $1000 just for the mixer/amp, speakers and cables, but it looks like it would eliminate a recording device.

Of course, you'd need stands, but those aren't too expensive for those small speakers. If you get a bag for the stands, you could put your mics and cables, (and maybe wireless receiver) in it, you could sling it over your shoulder, carry the PA in one hand, and your laptop/mp3 player/papers,etc. bag in the other.

You'll also need a good-sized USB flash drive to record to, but those are fairly cheap. Then, there's the mic. Can't suggest anything on that. A headset mic (or lavalier, as Remy suggested) would work, but you'll have to decide which kind, and how good.

Also, as Remy said, making it ALL wireless is impractical, and will add up, cost-wise. You'd need three separate transmitters strapped to your belt, and you'd have a mic on your tie (or on your head), wired to one, an MP3 player strapped to you, AND be carrying around the laptop...and then three receivers plugged into the PA (unless you get the mic/MP3 player/laptop transmitters ALL working at the same frequency, I guess? Can they do that, or will it confuse a receiver? I've only used a wireless guitar pack. Once. Many years ago.) Couldn't the laptop and MP3 player stay on the podium/stand/table, and wired direct to the nearby mixer/amp?

Anyway, that system should be enough power to be intelligible to 100 people gathered toward the front in a conference room. It will (apparently) record everything that goes through the mixer to the USB drive. When you are finished, you remove the drive, go back to the hotel, and dump it into the computer. If you don't need any REAL fancy further sound processing (just something basic) download the free "Audacity" program , and have at it.

What that extra cost may do is eliminate the need to buy a separate recording device, patching it in, setting it up, and then tearing it all down just to set up the recording device again later to connect to the computer to work on the recording. That could be hundreds of dollars just for the recording device (and possibly storage media), and thousands of dollars in accumulated time to deal with it all. Wouldn't you rather just pack everything up, toss the flash drive in your computer bag, and simply plug it in back at the hotel...instead of fishing out the recording device, plugging in the power cable, connecting it to the computer, powering it up, running through menus on the device (and syncing your computer) to get it to transfer...etc.? And THEN disconnecting it again, and packing it back up?

Get to the hotel, pull out the computer and flash drive, plug in the drive, save it to your "Presentations" folder, date "1-23-12, Denver Hyatt", and then go get dinner and drinks? You can deal with it later. Or, if you need to deal with it then, it's saved you time and trouble.

Anyway, you also indicated that you NEED an MP3 player, possibly. Which means you may not have one, yet? Is it possible that you could simply run the MP3's from your computer, eliminating another device and cables? Does an MP3 absolutely NEED to be playing at the same time as a (possibly) presentation that may also have sound...like a PowerPoint thing, or something? There are ways around that. The most obvious being to integrate the tune into the presentation so that it plays at precisely the right time, instead of you fumbling around squinting at a tiny iPod screen trying to find a load a tune. If it's just for pre/post/break music, just play it off the Media Player of your computer, and stop the Media Player when you start the presentation. Why add more possible confusion or points of possible failure? Plus, I may have just saved you another $100+. No MP3 player, no external recording device, no extra cables (and possibly media) for those...$$$ saved. That turns into inexpensive speaker stands and a mic. Possibly even a wireless mic.

Yeah, it'll likely be more than $600 no matter WHAT you do, if starting from scratch (except for the computer, of course, which you obviously already have).

Even if you buy a $300 portable PA system with just the mixer/amp and speakers, you'll still likely spend another $500-600+ on stands, cables, a wireless mic setup, a recorder, an MP3 player...and probably inferior quality from a cheaper brand. (Do yourself a favor and avoid the well-documented travails of Behringer's crappy-quality short-lived products. Remy...are you being ornery when you mention Behringer as a viable alternative?duh)

I've heard the Passport 300, and it did the job OK, for that kind of thing. Just don't expect any butt-shaking bass or eardrum-destroying dBs out of ANY of those for music...but I'm sure you don't.

Now for a caveat. I have no idea how WELL that Passport USB setup records, or the mixing options-to-USB. I have a feeling it's pretty much just mixed in the same proportion as what's coming through the speakers, instead of separate adjustable levels to the USB vs. the through the PA. That will probably be OK for what you are doing. I doubt you're going to try to be screaming over a Megadeth tune during your presentation. I also have no idea about transport functions for recording...as in, can you simply pause it during a break, and have it pick up again on the same file when un-paused? Do you have to stop it during a break, and create a new recording file to continue? How easy and quick is it to use? Those are things that can be discussed if this seems like an interesting idea. I'm not going to download the manual and pore over it at this time.

Anyway, these are just some things to consider. The FEWER things you have that can do the job, the less there is to shlep around, the less there is to connect and disconnect, and the fewer things there are to fail or cause intermittent problems.

Don't forget the speaker stand bag. You can probably fit the wireless rig/mic in there, AND don't forget at least a 20' extension cord (probably at least 16AWG) and a multi-outlet power strip (preferably with some surge-supression/filtering built in) that may also fit in there.

OK. Almost finished. You may want to find a music retailer near you that carries something like this. (I don't know if Fender is the only brand with the USB recorder?)
Take your laptop in with you, explain what you are trying to do...and see if they'll set you up with a demonstration? Have them demo the whole package, if they will. They may be able to set you up with the system, the wireless mic, the stands and bag, and whatever cables you need to connect EVERYTHING. If they are real cool, they may even stage it all as you would be arriving at the venue, and show you how fast it is to set up, record a few minutes of your computer (music, a test file...whatever) and vocals, stop everything, unplug, tear down and pack up. OH...just in case, if you do that, go ahead and take an empty USB flash drive with you (just so they can't claim they don't have one and can't show you that feature. You just say "WELL...it's lucky I brought one!")

They MAY even set you up with a tidy discount for the whole shebang? Ask them for 20% off all that. They probably won't go 20%, but they may counter with 10%. Then you may both agree when you counter back with 15%? Never know. Worth trying.

Just something to consider. May be a bit more expense than you expected, but no matter WHAT you do for anything close to adequate...it's going to be. At least something like this (if it's workable to you) may save extra devices. Fewer devices...fewer things to go wrong. Fewer devices..quicker setup and tear down. Fewer devices...less weight to lug around. Less setup and tear down time, and possibly less file transfer time...time is money. How much is your time worth, whether you are the boss of yourself, or you work for someone else? (If you work for someone else...explain this all to them, and put it on THEIR tab! They should realize that it may be worth a few hundred more to have a time-saving, more-reliable system from a relatively quality brand name, than going totally Chinese-junk, lousy-QC cheap.) if you work for someone else, is that after-presentation recording-handling time on YOUR time, or theirs? Look past "cheap and inexpensive", consider saving money by eliminating some items (if possible) to help cover others, and try to think through the options to consider intended AND unintended consequences down the road. Explore the possibilities! And simplify, when possible.

Just some thoughts.

Good luck,

Kapt.Krunch