You don't need a mixer - just a multichannel audio interface (eg FireStudio, Firepod, etc... avoid the Firebox because the pres aren't great and you'd need to get two more pres to get 4 channels) if your goal is to record. Mixers will take your four channels and mix to a stereo left & right - which means if you want to bring up a little snare or kick after you've recorded, it's going to be much tougher.Besides my bass, my kit is tuned just about perfectly how I want it. I guess I'll go with that then. One or two overheads, and 57/52 or d6 on the bass.
But: what about mixers?
GarageBand works fine with an audio interface. Don't know what the upper limit on channels is (I use Logic), but I know GB is fine with an interface.What? No, not true. I quote, from Garageband's help files:
"To record on multiple tracks, you need to have an audio interface with at least two input channels for recording."