How to direct sound through mixer

I have an Alesis Multimix 4 USB device, and I record podcasts with it. Sometimes I like to play snippets from a show, etc, and so far the only way I have been able to do this is the play the sound on itunes through external speakers and record it with Logic, but the sound quality is crappy as can be. Is there a way to feed itunes directly into my mixer so that it comes through my headphones on the mixer? If I can get itunes to feed into the mixer, I have a stereo mic (internal) hooked up where I can record the incoming sounds (kind of like putting Skype on Stereo and recording both my voice and someone else's voice). I would like to do this with iTunes. Any suggestions?

Macbook Pro using Mavericks, if that makes any difference, with current version of iTunes.