I want simultaneous multi-track recording. That M-Audio box you use only sends two channels at a time to Garageband, doesn't it?
I've just been looking at the M-Audio FastTrack Pro, which as far as I can see sends 4 channels to the PC via USB, but is somewhat more expensive than your $69 box. If I can convince myself it's worth spending 150 pounds on, that might be the solution.