Lane, (love that friggin' name!!!!!) for what you are attempting to accomplish, you would be well served with the SM-57 recommended by several already. For about a $100.00 you will be able to record on your Fostex just fine. Justa Picker is right on the mark (I have enjoyed this person's postings since the first minute they showed up on the Cat) for high end recording. But that is not what I hear you saying. I hear you saying that you are a person new to this and you have a Fostex 4 track and want to experiment and make recordings good enough to play for friends. In other words, you are just entering into this. Pick up an SM-57, you will be able to use it for live performance as well to mic your instrument.
Oh........yeah............and get ready to start spending money. Cuz once you start down this road, you will want more.