You definitely want a firewire interface if you're recording that many people live at once, and unless you're willing to spend a serious amount of money, it rules out digidesign and as such Pro Tools as your DAW. I'd go with logic personally, but virtually any DAW will be fine. I recently bought an Alesis IO14, which has 4 xlr/line ins and an adat in for future expansion. I'd say that to keep it simple, you'd want 8 xlr ins so that you can record live (there is the Alesis IO26, 8 xlr, 2 adats). Having said that, once you get into recording more, you might actually find yourself doing more overdubbing than you originally thought and might get away with the 4 ins. Depends on drum kit preference as well, you can get a drum kit sorted with 3 microphones if you position it right.
If you have got monitors then you obviously want a decent set out of outputs, then you can send different outs to each monitor should band members want that. If you are using monitors properly, that also means you could use keyboards for midi and be able to hear it in the monitor mix.
Good luck.
