Just saw this post.
I have a Sonos ZP90 and have been using it with an Arcam rDac for the last week. I had previously tried using my MF V-Dac with the Sonos but found it provided no benefit. The sound from the analogue out of the ZP90 is pretty good.
I managed to get an rDac on loan and it provides a clear benefit. In my system the sound is fuller and more spacious. I previously was always aware I was not listening to a CD through my Leema Antilla II. Now I find that I suddenly find myself stopping whatever I am doing and listening to the music in the same way I did with the Antilla.
On a back to back comparison with the Antilla, the CD player still has a larger sound stage and a bit more attack, but in terms of bass, mid and treble and sound signature the Sonos rDac combo is really very good.
I have now bought the rDac.
I am using WAV files on a NAS drive, the Sonos is wired to the router, Sonos is connected to rDac via Atlas Compass coax, the rDac is connected to the pre with Kimber KCAG interconnects.
I also use a regulated power supply from Maplins in preference to the switch mode wall wart provided. To my ears it improves the sound. Don't know if its the supply that improves the rDac or the switch mode wall wart that degrades the rest of the hifi.