Quite frankly, I have very low expertise. Instead of trying to output to the computer's soundcard (in this case, the Macbook pro's) I am trying to make all input and output sound originate in the M-Audio Profire 610. I know it is recognized by the program, but difficulty is in figuring out how to configure it so all sound is "routed" (for lack of a better word) through that micPre/interface.
Alright, here's the quick and dirty tour through audio hardware setup in Audition CS5.5. First, make sure that you're seeing your hardware listed in the audio hardware preferences dialog.
If you have an ASIO driver available, use it. You'll have lower latency and better performance. If you don't have an ASIO driver for your device, check with your manufacturer to see if they have one available, or choose MME under Device Class and make sure that you select your device's inputs/ouputs. If you don't see your device here, check to see that you have it listed in the Windows Sound control panel.
You can set the preferred inputs and outputs of your device as defaults in the Audio Channel Mapping dialog:
When you're in multitrack view, you can set your device's inputs for each track, and assign the outputs for the Master to your device's outputs, or the Defaults that you specified in Audio Channel Mapping.
Once you've made sure your device was recognized by the system, and that you've chosen your device's ins/outs in the places I've shown here, then you're all set. You should no longer be sending sound through your computer's default sound system (eg. soundcard, onboard audio).
The screenshots here are just some quick grabs from my home system, so where you see "Saffire Pro" that's where you'd expect to see your hardware listed.