ANY time you can buy a Shure SM81 or an Audio Technica 4033 for 150 clams you should do it.

Both of these mics are a next big step in starting a mic collection. The 4040 is a nice mic also and I have no experience with the Se stuff, though I hear from people I trust that they sound very good.

As far as the Heil or the ADK's these are also quality mics. And a studio would be benefitted by having all of them on their equipment list.

As for WHAT would be next for YOU personally, you need to assess what your going to be doing the MOST of in your future recording plans in order to choose.
Mind you....one SM57 is not enough....you should have three minimum...And a very important aspect to consider is how many instruments you will be recording at one time. If you are looking at a complete drum kit , then you are going to need several mics going at a time......minimum four, unless you have a stellar recording room and then two will do. At a minimum youre going to mic a kick-Heil PR40=killer kick mic....Snare-SM57=industry standard.....overheads-two SM81's or two AT4033's.

Guitar cabinets-SM57...yeah theres 'others' but are they 'better'???

Percussion=SM81 or 4033....theres really not much either of these mics cant do well.....

Bass= Sans Amp Bass Driver.....save yourself the problems involved with trying to get a decent bass sound out of questionable equipment from the beginning....you can 'graduate' from this when you get better.

Vocals. A Hamburg and a Heil PR40 are enough to handle a LOT of vocalists without problems.

You can do a lot without a lot if you get the right stuff to begin with.

Dave's right - if they are in good shape, you should snap up as many SM81s as they will sell you at $150. (Be aware that there are counterfeit mics out there. Be careful.) Both of the AT mics are a steal at that price as well, but not as good a deal as the SM81. One thing I'd add to what Dave said (though I guess he implied it) is to look for the opportunity to buy a pair at some point for overheads or stereo micing acoustic guitar or percussion. I've had better luck with SDCs than LDCs as overheads when using four mics for drums, but there are lots of people using LDCs out there it would be good to pick up the a pair of, say, the 4033s if they are available.

If you can, don't be too quick to get enough mics to record five pieces. Take your time; look for deals; buy quality. (Quality doesn't mean the most expensive. Every time you double the price point the quality difference gets more subtle. It's just not worth buying in at the bottom level for the savings compared to the next level or two.) You can easily go broke in this game "climbing the ladder," buying cheap gear, getting rid of it for slightly better gear, moving up a little at a time. Better to start a plateau and stick with it until you have the money to make a pretty big jump.

Thanks. I've already inquired about the SM81, but no response yet. I really want to get some good acoustic tracks down, and from what I've heard these clean house on acoustic guitar, especially for darker, heavier sounds (basically, exactly what I'm looking for tone wise).

If I'm impressed I will eventually get another and use them as a stereo pair, for acoustic, overheads, and I think they'll do well on some of that wooden percussion too.

And, even if this deal falls through, I found another for $180, but he says IN THE AD that that's what he paid for it (stupid), so i believe I could negotiate down to $150.