Tried this out lastnight.
Using Media Center X I had to convert my divx files using Wii Video 9 in order to even see the files. MP3 playback still does not work for the wii.
Using Orb I could play divx and mp3 files but it looks like it streams from the internet even though my PC is connected to the same router.
When playing divx files there was a big loss in quality.