FWIW, different revisions of the 323's firmware provide different UPnP functionality. I can't remember back to 1.06 but I'm sure you can search the forums. IIRC, there was very limited support in 1.06 for what the 323 would stream. However in 1.08 the 323 serves up:
.m4a
.mp3
.mp4 (h.264 & .m4a audio)
.m2ts (h.264/h.263/h.262 & .mp3, .m4a, or .ac3 audio)
.avi (h.263/h.262 & .mp3 or .ac3 audio)
.mpg
.mpeg
.wmv
.wma
.iso
Don't ask me about iso, lol, I've never seen it work. My PS3 seems to have no problems playing the remaining formats. The PS3 is a DLNA-certified device as well.