Okay, say you're set on using your computer to record...
How many sources are you expecting to record? Do you want each source recorded seperately onto it's own track for mixing later?
There's a few main features to look for in an interface.
1. the number of inputs. Breaks down into number of Preamps and Line out. If you have more mic sources than preamps you'll need to buy preamps in addition to the interface to amplify your mics to line level. This won't be too big of a deal, you can use the behri board's preamps in a pinch.
2. the number of tracks that can be recorded simultaneously, for example the Lexicon Omega only records 4 channels at once, likely not enough to do a full band all at once.
3. the type of connectivity, USB or Firewire or PCI. USB is usually cheaper, but because of the lower transfer rate, you won't get as many simultaneous tracks in/out. If you are looking to record a full band, you'll probably have to look at firewire interfaces (make sure your computer and O/S supports firewire). PCI requires installation directly into your computer and isn't "plug and play" so I wouldn't recommend that
4. This is mostly governed by the software you choose, but total track count. If you plan on overdubbing a ton, this may become important.
5. MIDI capability. Looks like you already have a MIDI interface, so this won't be too big a deal.
There's probably other stuff too, but that'll get you started looking.
How much are you looking to spend? Here's a few products to check out.
1.
Digidesign 002R.
4 pre's, 4 line inputs. Records 8 simultaneously (expandable to 18 with addidional H/W). Comes with Protools LE. I'm currently using this setup and have no complaints.
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/704168/
2. Presonus Firepod
8 preamps, switchable to line. 8 simult tracks. comes with Cubase LE
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/184131/
3.
Tascam FW1082
4 pres, 4 line. Comes with a control surface, Cubasis LE and
Gigastudio 3 LE
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/706931/