Tascam Or Quattro, Help Needed Options

[JoeS]

I am looking to set up a home studio, and am trying to understand all that's involved. I have started collecting elements slowly and have a Mackie 1202, condenser mic, and Cubase VST. I will using this on a 366 mHz iBook with 196 RAM and 10 gb drive. Yes, I realize I might need a Firewire hard drive at some point. And I'll probably be purchasing a desktop G4 fairly soon. I'll be recording instrumentals (solo, multi-tracking) on guitar, flute and keyboard. I'd like to have the option of including MIDI at some point.
I assume my next puchase needs to be a USB A/D/A converter. I'd like to keep costs around $250-300 (probably by buying used).
I've been checking out the Midiman Quattro and the Tascam 428. Am I on the right track regarding what I need to get started? Do these perform similar functions?
Any advice or suggestions would be greatly appreciated.
Thanks.
Joe S.

[JoeS]

Thanks for the advice. Very helpful.
As a result, I have been looking more carefully at the Edirol products. The UA-20 seems like a good option for me. Both audio and MIDI, low cost, and 24 bit processing (see, I did learn something from previous posts). The only problem is finding one.
Joe S