Using a USB2.0 Mixer with Audio Interface in GB '09 vs a A/I ?

Hello,

I am posting re: using a USB 2.0 Mixer (example Allen&Heath Zed Series with or without effects, Mackie USB mixers, etc, to use

rather than a Audio Interface (Which I have done in the past, though one I have did not keep drivers updated past OSX 10.5

Leopard, I have bought and returned a Firewire 400 and a USB 2.0 Audio Interface(s) in the past 10 months, so No recording

I can use a Podxt to get Guitar in via USB but not XLR mics (Vocal or Amp mic's) I have read and read and spoke with people

and get a variety of answers, I am inquiring is this a workable way to get both 1/4 HI-Z inputs (Guitar or Bass) XLR Mics

and line ins to the mixer and USB 2.0 to/from my iMac? I am just looking at going in a different direction, and using Garageband

the Audio Interfaces I had bought both had on screen mixer-routing (which drove me crazy and to me un needed)

Prior I used a bus powered Tascam US-122, I do want extrenal power (and both Audio Interfaces did that I bought and returned)

I just need a basic sound in-sound out etc, with decent preamps , I have Mics, Guitars, Monitors, MIDI Keyboard, etc

just lacking the source in, (I also wish to avoid headphone monitoring due to ear issues which I do not desire to further

aggrevate, I hope this makes sense, 😕

Thanks,

diamondblues