Going to try digital

Check out NAD M32 (with BluOs card). Sounds great, flexible and upgradable. 

In a setup where Roon core runs on a noisy PC, connects thru ethernet to a Cisco wifi router, and the optimized audio PC receiving from Roon on HQP also connects thru ethernet to the Cisco, would you recommend using just one EMO-EN70e at the audio PC input? Or more, or elsewhere? How about a linear power supply on the Cisco?

First of all, the only thing that matters is the router, not the PC. Don’t waste money on the router, it needs mods.

This is what will deliver great results, even with a Sonos:

1) AQVOX switch added to the router
2) 0.5m Wireworld Platinum Ethernet cable from switch to isolator
3) EMO EN-70e isolator
4) 1.5-2m Wireworld Platinum Ethernet cable from isolator to PC

Steve N.

Empirical Audio

I don’t have a high-end stereo yet and will soon install a Raspberry Pi as a cheap streaming server. Those can be found for < $100 but you may need some technical knowledge to set it up.

Been there, done that.  The Digione card is pretty good, expecially the new one.  My Interchange still beats it.  You can see jitter measurements on RPi here:

https://www.audiocircle.com/index.php?topic=154299.0 

Steve N.
Empirical Audio

"1) AQVOX switch added to the router
2) 0.5m Wireworld Platinum Ethernet cable from switch to isolator
3) EMO EN-70e isolator
4) 1.5-2m Wireworld Platinum Ethernet cable from isolator to PC"

Steve,

That’s $2.5 to 3k worth. I don’t doubt is the cutting edge, but how can I get 50% of the improvement for 25% of the cost? What’s the pecking order if prioritizing this list?

Change the Wireworld silver cables to copper with silver plating.  That will save a lot of money.  Not as analog, but very good.