After seeing Apple's airtunes setup I wanted something like it. It is basically a wireless device that lets itunes play through it as if the sound card was connected to the computer.
I put gentoox on my xbox. At startup I have esd (a sound server) start, associate with the digital output of the xbox and accept connections from the network. On my laptop I set gstreamer to output via esd, and to the host of the xbox. Now when I play anything through Rhythmbox the audio gets outputted through the xbox. Very slick.
Just thought I'd put this out there. It is a very simple solution but I couldn't find anyone else that had come up with it.
dan