I use an M-Audio 610 that I bought used and it works fine. I also have a Presonus Firepod I bought used with lots of inputs and it sounds good. Both are firewire though. I had a cheap Omega with USB it it also sounded quite good.
Digital to Audio converters are quite good these days, which makes me think that buying something based on the rest of its features that you might like is a good idea (including software bundles). Some units let you side chain out into other outboard gear before it hits the converters, and I think that is very helpful, esp. if you need a compressor.
I use a F-2B for a tube pre on my bass and it sounds great and I get a great bass tone that way, even better than my F-1X.
I am surprised Alembic does not market them more that way, as they work fine. It also sounds great with acoustic-electric guitar.
Garage band is great for Mac, I use Sonar 8.5 on a PC, but there was a steep learning curve when I first got it.