I am able to get DSD files to play from Asset uPnP via the Pro Plus' digital outputs:
As DSD
Serve .dsf files as DoP since I have a DoP compatible DAC. I did this for just the Wiim control point since I have other streamers that can handle the files natively. However, as another member noted in another thread, I get a loud crack/pop at the beginning of each track. I have filed a support ticket.
As WAV
Serve .dsf files as WAV, resulting in a 24/88 render. No cracks/pops.
As LPCM
No dice - my DAC apparently can't do it.
My end game would be to have playlists of mixed file types just play with little to no down-sampling. This would be a win for Wiim since they're already ahead of Bluesound and Sonos in file compatibility.