Have a look at this:
http://www.slimdevices.com/The only thing it can't do is use MC's UPnP server.
Last Christmas, having tried one or two of these type of units, I found the above and have been so pleased with it I now have 3 in different rooms! You will find the support and ongoing development up to the standard you get here.
I have used MJ/MC since v7 but no longer use it to play music only to manage the library/playlists, etc. as 'SlimServer' does not have any real music management features.
I used to have all my music in APE format for MC but as the 'SqueezeBox' has native FLAC decoding I used MC to convert all my files to FLAC. It also has native MP3 decoding so you will have no problems.
The combination of MC to manage the music and 'SqueezeBox' to play it is terrific. I just wish the SB could access the MC library directly.
Hope this helps.
David