I had an unused Mini-ITX computer which I can make silent (by removing the fan) as long as it isn't doing anything too intensive, and some spare speakers from a broken CD player... so I put together some remote speakers to play music on.
With some cheap bamboo cane and tie wraps I've mounted them at the head of my bed. The server boots over the HomePlug network allowing MPD to connect to it. I'll add a wireless remote control soon.
I seem to have been too quick to use the mini-itx box for something... getting everything to automatically power off at the end of the playlist isn't trivial. I can actually run the audio cable into the next room where I have an otherwise unused sound card output available. (The remote control will communicate using RF and should work through the wall).
Perhaps I'll try making it into an almost-instant-on thin client instead.