I use the Fire Studio Project for mobile live recording, actually these days I am using two daisy chained. It is a very adequate unit for this purpose. Eight channels might be a little restrictive depending on the groups you are recording. IIRC from your posts in live sound you are using your aux mixes for monitoring purposes, but do you have one aux out not in use? The reason I ask is that if you can submix drums sending them to one or two channels (stereo) then eight channels might easily be sufficient. The interface could easily be routed from inserts with specially wired 1/4" plugs or by inserting the tip part way into the insert (risky in mobile sound due to the fact that they can easily be jarred.) I think the biggest hurdle here is defining how you might typically use 8 channels, drums (how many mics), 2 guitars, bass, keyboards, 2 or 3 vocals, horns, harmonica, I'm sure you get the idea. When I first started I had at my disposal a line mixer and often subbed the drums into stereo and took it in two channel, but you are at the mercy of whatever mix you choose and if you needed to buy one it is approx. half the cost of adding a second Studio Project, if you have the processing power definitely a better way to go.

As far as the computer you really need an a second (external?) drive and if your computer does not have a Texas Instrument Fire wire port a PCI card with a TI chip (Presonus requirement.) You do not need to upgrade your soundcard as it is not in the recording or monitoring chain. You really should post the computer specs in the presales section of the Presonus Forum to be certain that it is adequate to do what you envision.

I was thinking and you did not really ask this but a much less expensive alternative is to use a 2 channel USB interface from the rec out of the Yamaha which would give you a "decent" recording of your mix at the board. This option does not leave you very much room in regards to post production. It really depends on what you are looking for and your definition of decent.

I thought about the 2 channel/rec out option, but I'd like a little more post production flexibility. The room of course is a bit different than what the recorder would hear. So I'll stick with the Presonus, glad you have and enjoy one!

I do actually have an external hard drive, with about 250gig free space. My computer doesnt have a firewire port, but I believe I need an ExpressCard to Firewire adapter (since my computer has an ExpressCard slot), correct? Something like this? :
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4276631&CatId=510
I plan to use this same computer to mix with, I still dont need an upgraded sound card or anything? Heres what I can tell you about my computer right now: Intel Core 2 Duo T7100 @ 1.8GHz, 2GB Memory, Vista 32bit

My current mixer only has to Aux outs (which is why I need to upgrade to the MG24), so that only leaves me two monitor mixes. Normally, the venues I'm at, the only things I have gong through my board are: 2 guitars, bass, kick, 3 vocals. I could had an overhead condenser on the drums, and that'd put me at 8. I should be able to get a fairly good mix with that I would think.

On another note, post production wise, I have a pair of active studio monitors. How to do these get worked into the system. To me, I need the following to make this whole thing work: Computer, Firewire adapter, studio monitors, and proper cables to go from the insert on the mixer channels to the presonus. Speaking of which, what cables exactly are those that I need, insert wise?

Thanks a ton!!

You absolutely do not need to do anything with the soundcard. All monitoring/headphone access is done through the Presonus. Your powered monitors hook up directly via balanced cables. Your inserts are TRS one sends the other returns and I can't off hand recall which does what. Just post a question in the forum re: insert cables for recording.
The Firewire card must have a Texas Instrument chip this one does but I am not sure if it is the right one because I don't have a laptop.
Link removed
A single OH might work.
You will need to tweak your computer some for recording. Here is a thread but I don't use Vista
http://www.sound-unsound.com/forums/tutorials/1265-tweaking-vista-music-production.html

Good links, thanks. I should probably go to the presonus forums to make sure I get the right firewire card. I appreciate the help!