Aurender music servers: higher priced ones sonically better?

The problem is PCs are simply not created with noise reduction and power conditioning in mind.

Correct.  Which is why i advocate simply isolating it and creating a dedicated low noise power supply on the "clean"side and allowing the Mac streamer to be dirty.  trying to fix the computer will have diminishing returns (but running of battery makes  a huge difference, with lots of limitations).  This is why i wanted to know precisely what you tried and didn't.

NUCs are actually quite good if dedicated and with dedicated,and split/isolated power.  RPis make good bridges (but start with the Pi4 or you will fight a lot of architectural issues).  I mean, have you looked at what's inside the box of many streamers?  Often a NUC or a Pi (as embedded).

itsjustme
Sorry went by what I was told about  Roon should have read it for myself if you could post a link for the post so I can read it 
thanks for the good comments on my system 

i don't know if i can find my old post - its a needle in the haystack. You might search on my user name.  But most of it is blocking and tackling - clean power, clean grounds, isolation, keeping nosy digital devices away from sensitive analog ones, keeping the processing distributed (just like Roon recommends), etc.

That said, Roon is a frustratingly complex, but very powerful streaming solution.  It is sold as a full server (Nucleus) or as software that you cna load on your computer or build a dedicated server as I did - but in the end, its a streaming server with vastly more capabilities than anything you can buy from "fill in the blank". In fact some high end servers ARE in fact Roon, embedded.

Unlike most streaming servers you can serve multiple independent zones (rooms, systems), or synchronize them - AND control the timing priority for those synched zones.  For each, with enough computer power, you can correct for room abnormalities, although this is a needlessly difficult process (like much of Roon IMO).

I did look at my own history... and can't find the needle int he haystack.  Sorry.