I’m not sure why you are using the Sonos at all? I use a small form Asus Vivo PC that outputs optical to my dac. I know its not PMC ready but I do have the usb for that (i know your trying to get away from that). I’m just wondering what the Sonos connect does for you other then add another box in the chain. I would assume the mac will do similar if not maybe its the week link and a dedicated music server is the better choice.
I stream Tidal / Roon from the PC app on my Vivo PC and the PC connects to my network and NAS so I don’t need another box.
I do like the Blue sound node 2 for simplicity and user interface so I may go that way maybe that’s something to look at. I listened to a blue sound vault two as well as a Sonos in my system as my friends shop sells both and the Blue sound vault 2 is far better then the sonos for sound.
I'd be interested to see what you end up with as i'm also considering a Digital change / upgrade.