Figured it out . I have my Xbox 360 hooked up to a 19" Gateway widescreen HD flat panel monitor (basically a widescreen computer monitor) on a desk right next to my MBP. I'm running the Xbox audio through the Line-In on the MBP and using the application LineIn that lets me play the audio through my external speakers while they're hooked up to my MBP. So instead of switching cables, I just turn off/on the application LineIn to have the sound come from either my MBP or 360. Perfect setup IMO, minus the fact that the 360 is SO LOUD.