Well, it's my ultimate goal to get a different piece of software on the Central, perhaps a stripped down (video stuff removed) version of Freevo. I have written plugins for Freevo before and it would be pretty simple to get it to read the music fid files. In addition, Freevo currently supports being both a uPnP server AND a client.
However, I don't think it will run well at 16M RAM. I'm hoping to get some help on upgrading my central to 32M, so if you know anything about hardware hacking, please let me know.