But if you are also an “I trust my ears” person, you have to give up one or the other. I don’t trust my ears, because I don’t trust my brain.
There is one clock that really matters, the DAC’s. For async USB, it’s 100% the DAC. For sync interfaces like S/PDIF or AES, the source’s clock is also involved, but good DACs always eliminate input jitter and don’t depend on the source’s timing. Network clocks are always 100% irrelevant.
You asked:
You could go with a low cost Roon Ready bridge/streamer. There are a few models that are particularly popular with Roon customers, like the Bluesound Node and the WiiM devices. They all have optical outs (I think) People here in Community have been very happy with them. I’ve used both and had no complaints with either. I recently put a WiiM Pro Plus in my daughter’s room connected to a pair of speakers so she can enjoy Roon. Speaking of…
Another possible solution for your second room system could be a nice pair of wireless speakers. (I’m not sure if this is an acceptable approach since you spelled out “into a good quality self-contained hifi system” but also say you have some difficulty understanding what does what and not neccisarily that it MUST BE a toslink-based solution.)
If speakers are an option, you could look for a Roon Ready set (which could be paired with your RR Novafidelity) or choose a model that works with Airplay, or Chromecast.
If I were you, I’d search out a Roon Ready set — so I could do multiroom with your existing Roon Ready stuffy and take advantage of RAAT’s Hi-Res streaming capability. There’s a lively speakers discussion here you can explore. Thankfully, Roon works with a wide range of devices so there’s plenty of options to choose from.
Anecdotally, I’ve plugged an AudioQuest Dragonfly Red directly into the USB output of a Nucleus Rev. 1 and then into an affordable pair of Klipsch powered speakers and gotten surprisingly good sound. Easily on-par with a high-end bridge device I was reviewing at the time when going into the same speakers.
Some of the opinions/warnings about noise-ridden USB connections have to be balanced against whether or not you can actually hear it. After all, you’ll be using your ears to listen to your system, if you don’t detect significant sonic differences then does their existence, real or not, really impact your enjoyment of music? I can’t see (or hear) how it would.
Incidentally, I use a Dragonfly Red plugged into the USB output of my NUC, then coupled with a Sennheiser HD560S and the sound is superb (I know this is subjective, but it is for my ears, especially at night when the room is so silent)
I agree regarding the Dragonfly’s being great. I have the Cobalt with a cheap as chips pair of Sony WH1000-xm5s and I thoroughly enjoy the combination.
Regards Andrew
+100!! 
This point often seems missed in these discussions.
Your better dacs use balanced outputs and usb is the worst input to use into a dac.
USB is actually the best. It’s got a bad reputation because marketing.
Well that didn’t take long. See what I mean? 
Some of the best dacs don’t include usb input. Go read up on the Berkeley dac, which doesn’t include usb, and they state usb is very noisy. So they make a $5000 box for usb to clean up the noise and other artifacts and then uses a different protocol into their dac.
Read up on audiophiles/manufacturers reviews on how Ethernet and i2s sound so much better. Why are there hundreds of gimmick products to make usb sound better?
Notice something?
We don’t know if the OP has an issue with noise in his current/future setup though, we can only point out that there might be one and he has to figure out what works best for him. The rest is up to the OP and his “respected local HiFi retailer”.
The “respected retailer” already gave the OP false information.
I’m immensely grateful to all those that have taken the time to make suggestions. There’s a lot of useful information in there. Slightly amused by the peppering of TLAs (three letter abbreviations), some of which I understand, but many I don’t. However, I what on earth is ‘the OP’ - apparently me?
Yes you, the Original Poster.
TLAs (three letter abbreviations) are manageable, but TLAs (two letter abbreviations) are simply impossible.
Suedkiez- I do, even when a manufacturer makes a $5000 product to better the sound quality of usb, that tells me usb is flawed and it takes thousands of $$$ to try to make it better, and even then it can’t compare to Ethernet and i2s. Thanks for pointing this out!
Again with the funny
What that tells me is that manufacturers keep coming up with gimmicks (like I2S) so that people keep “upgrading” their gear. (When the next gimmick is found, I2S will of course be horribly flawed.) Engineers keep telling you that’s ■■, but you choose to believe the interested party. Otherwise, you’d have to admit you wasted your money and what you thought you heard was not there. I guess it’s easier to defend your choices with circumstantial “evidence” about the number of gimmicks, their price and the number of people who believe in them.
I know this won’t change your mind, but hopefully others will be better advised.
What’s I2S?
