First of all, you'll want something with balanced inputs, using 1/4" and/or RCA jacks via breakout cables. For audio recording you want to avoid the standard 1/8"-supporting crap.
Next, you'll want to have a good signal/noise ratio on
input. The output s/n ratio is meaningless.
And of course, you'll want to get something from a trusted manufacturer. Echo and m-audio are both solid companies.
This one ($164 shipped) looks decent, although I admit I've never used it, personally. Something like
this ($199 shipped) will perform better, but may not be absolutely necessary for the kind of work you'll do. If you can't afford either, you could try something like
this ($95 shipped), but I strongly suggest avoiding any card without breakout cables.
EDIT: Ordinary sound cards (such as the SoundBlaster Audigy series) will record music, and should provide decent frequency response, but they will almost certainly add a rather loud noise floor. The added noise is easily amplified when you apply such effects as compression or equalization. Since, as a rock band, you will be using those effects quite often, you'll definitely crave something better than an Audigy.