Thanks for the feedback guys!
turtle beach makes a very nice usb sound dongle. It even has optical spdif out so you'd be able to feed a high-end amplifier when needed.
That sounds good. Optical would keep the whole chain digital until the amp.
If you are going to do tcp/ip audio distro, look at some of the higher-end components from Denon, Onkyo, etc. They have models that connect to ethernet and might be 'remote controllable'.
Well in my kitchen or bedroom I'm more than satisfied with a single source audio - as long as it's MC-based! I have a big Denon AV amp from a few generations back in my living, which I can control via RS-232 in Girder on the same PC that I run MC on.
Also look in to how you would send/receive IR remote control commands. This is also possible within the setup you imagine. As is lighting control.
Part of my plan is that I won't need IR for control of MC. IR can't send any data back... xpTunes, Rivermote, Netremote all provide ways to not send commands, but also receive feedback (e.g. browse a playlist) and no need of turning on a TV
Simplifying things, there are any number of simple network devices that are designed to do what you want out of the box. And they cost at or less than the $300 per room price you seem to be willing to pay.
Well closest I've seen to what I want is the Squeezebox Duet or Sonos, which are not really cheaper... And another downside is that they're not really integrated well into MC, they would have limited access to its resources via UPnP and Sonos even has to fall back on manual exports of playlists...
Where do they put the play control? At the end point or back at the MediaCenter machine?
I like the idea of having one PC doing all the MC playback, transmit audio over network/USB and control via wireless devices. This way you can also control what's playing in, say, the kitchen on the PC running MC as well as with any phone, Ipod Toutch etc whatever is most convenient.