Hi Jonathan,
Possibly I don't have any real input for you, but I can always try ...
I feel that for 50% of the "challenge" you may think upside down. But, this is already hard for myself to pose correctly. So :
If you run XXHighEnd on what we'd call the Audio PC, then this PC containts totally nothing. Btw I am pretty sure that you do similar with the iSCSI boot (but it is not 100% the same, technically). Thus :
OS boots from RAM and now everything and all can be disconnected. This includes the Network.
When music data is needed, the network is connected (software wise) and the files are loaded in RAM of the Audio PC (this is the PC which plays the music and where the DAC is connected to). After that, network is disconnected again.
Side note : when RDC is used then a small portion of the network needs to stay alive - let's solve that one day.
When music is playing, it is XXEngine3.exe which is active. Nothing else. This situation is as lean as I could make it. Notice though that XXEngine3 is running on the Audio PC itself which may feel counter productive because others do this some other way around : they control the Audio PC on a distance, the player GUI running on that PC at the distance. In our case the player GUI runs on the Audio PC itself, but is completely killed when music starts. Only a small hook to keyboard shortcuts remain, for control.
So intead of controlling the Audio engine from a distance, there is no control needed because all else on the Audio PC is killed and the remaining situation is the same as the one you're thinking of : the audio engine running on its own in a
dedicated PC (because it just made itself into that).
The way the music is loaded is exactly the same as in your thinking (I suppose) with the difference perhaps that it is not pushed but pulled by the Audio PC itself. When ? well, when no music is playing - you being in (GUI) control again and thus harmless.
The mistake you may be making is the
thinking that the Audio "processor" must be small and not-consuming etc. etc. ... WRONG. Wrong because nobody has ever been able to proove that anything small sounded for the better; the contrary - it is deep-sh*t (and should be your situation as of now, no matter you like it very much).
So my approach is - and always has been the other way around : use that super machine which actually is not needed, with the notice that when it drives a 100 miles/hour it still is in 5 seconds at 200 miles/hour. This, while your PC barely gets at 100 at all.
And the more this strategy is put through, the better the sound is (which is also related to what can be done under the hood for processor cores etc.).
In the end it is the combination, like the 20++ core processor system only consumes 30Watts and that even with linear PSU.
You did try Minimized OS, right ? because it is all about that.
Maybe I should also ask about Unattended Playback because that is what I implicitly talked about (no GUI).
If I am all the way off, just tell me !
And of course don't hesitate in being creative and improve. It's all about that you know. So the text above is only trying to give you some context of the current situation,
Regards,
Peter