Just want to report that I have been using an Oppo 103 as a transport from PC/ethernet to external DAC via coax out and it sounds outstanding. Why, I don't know. For anyone following my other threads recently, I would rank the sound quality much higher than the F-1/XU208 usb to spdif converters. No, it is not as good as the RedNet I've discussed in this circle - the RedNet is just a whole other league altogether - *but* the Oppo is just as satisfying. Again, this is using the ethernet connection. I've tested the usb on the Oppo and it sounds like, well, usb.
However, I don't believe this performance necessarily applies to all Oppo models. I also ordered a 103D, to try out the Darbee and was disappointed to find the playback quality was not as good. It sounded more like what one would expect from a media player, a little bright and 2-dimensional; good, but not great. I played with all the settings, but the result was the same. Oppo got something right with the regular 103. Coincidentally there is a diyaudio member who just started selling custom linear supplies and clock for the Oppos with impressive specs (no, not like Modwright which is focused on analog playback), so I'll be do that next.
Just want to put this out there, because I couldn't find any real feedback online from anyone using this route for playback. I think the 103 may be a hidden gem in this regard.
Downside is you can not use UPnp/DLNA for the ethernet connection, so you have to use the Oppo interface to access files not your PC.