The SansAmp is probably the cheapest, because it only has overdrive/distortion. I believe the others have multi-effects, which is cool....but Cool Edit Pro has effects that you can add, so you might not need the multi-effect type pedal if you're trying to go cheap. I got my GT2 off of ebay a year or so ago for around $80 (with power adapter).
I simply ran my guitars and my bass through my SansAmp into the mic jack on my laptop (using a 1/4" to 3.5mm adapter). Set the recording levels and recorded. I don't have any of it online, but I've had several compliments on the sound quality of both the Sansamp distortion and the cd quality. My laptop has a stock soundcard too.
Here's a liitle tip from experience on the drums. If you are using a drum program like Fruity Loops, write your drum part, but then save each individual drum and cymbal track as a separate wav. That way you can eq each one to your taste when mixing. I put the bass drum tracks down twice. I push the mid and treble up on one of them and mix them - and I can knock stuff off the shelves when I run it through my stereo. The way it should be!
Vocals have got me though. I tried running my mic through my SansAmp, but got way too much 60 cycle hum. The only decent vocal recording I've been able to achieve so far has been from a standard computer mic and LOTS of effects and filters.
Oh, and just to add to your indecision.....don't forget to check out the J Station too!
