I realize this is a pretty old thread, but I did today manage to get this done.

For a renderer: GMediaRender running on Debian Squeeze on a 1998 Dell laptop, using Alsa to drive a USB>S/PDIF converter which feeds a DAC connected to the stereo. The Debian install has no graphic UI, just a command line (and an SSH server so I can open a shell on it from the PC). The necessary packages beyond the base install were Alsa, GStreamer, libupnp.

For a media server: MediaMonkey version 4 (still in beta), which I've been using as my library and player on the PC for a while. (The PC has a direct S/PDIF connection to the same DAC.)

It took a lot of fiddling, of course, because Debian doesn't care if you understand what's going on. I had to install an MP3 plugin for gstreamer (I made my own build of the Fluendo one, so I'm legal); I had to build GMediaRender; I had to change the Alsa defaults to point to the USB-audio instead of the PC speaker.

The big disappointment is, even tho the data should be going direct from server to renderer, MediaStreamer won't allow anything but an MP3 stream. MediaMonkey will convert to MP3 on the fly (say, M4A, which isn't supported on my Debian box at the moment) and that will play. But I want my FLACs to go across as FLAC. FLACs and OGGs stored on the Debian box will play direct from GStreamer, but when selected via MediaStreamer, GMediaRender reports "Error: Stream contains no data" despite seeming to correclty recognize the data type.

Even when successfully playing an MP3 to the external renderer, the progress bar in MediaStreamer is broken: it never progresses, the time display keeps switching from 0:00 to 0:01 to 0:00 to 0:01...

For some reason, tho, I can't get the MP3 to play thru MediaStreamer to the N800's own speakers. It shows "buffering" and advances the progress bar as you'd expect, but no sound. Canola plays thru the speakers fine.

MediaMonkey doesn't have Control Point capability, but it's planned for a release after 4.0 gets out. I'm eager to see if it works better than MediaStreamer.

EDIT: shortly after I posted, I tried again to get sound to play thru the speakers and it did. Not sure what the hangup was.