Infiniteloop said:
Some people will tell you that as it's all digital, there cannot possibly be any difference in SQ.
.. and I would suggest you ignore those people.
The connect is a couple of generations old. It suffers from poor jitter performance, and has never been considered the pinnacle of audio performance. If you feed it into a DAC that has jitter mitigation circuitry then it is as good as any other digital source, but as (I believe) you are using its analogue outputs, then you may well be able to do better.
Jitter aside, as pointed out above, much of the performance of the digital audio system has nothing to do with digital, but is driven by the analogue filters and circuitry after the digital to analogue converter chip inside the player. Here again, the connect isn't considered the best.
If you want to hang on to the convenience that Sonos brings, but want to see if you can improve the sound, I would suggest feeding the digital output of the connect into a good, modern DAC and then into your Cyrus. You should get the best of both worlds, streaming and high quality.