It sounds like you want a music streamer box that also gives you Youtube and other non traditional music sources? Is that why a more standard streamer won’t work for you?
My take is that it’s an interesting idea but I think the weak point is that this is a pc. You have a motherboard that generates all kinds of noise and everything runs through it. You are adding things at the edges to fix the problem in the middle, if you see what I mean? Personally I see computers as an inherently dirty signal, rather than trying to make it less bad and adding endless expensive components where you still ending up needing to clean the signal on exit.
I personally think you would be better off with a single exit solution such as an external reclocker: either a consumer DDC; or a prosumer device like a Mutec. For the same money as these parts you could have a very good quality reclocker/ddc that deals with all the issues of using a PC as a sound source and money left over for your source device.
You could then go with an off the shelf NUC running windows and either access it directly or using RDP from another PC as mentioned above. Alternatively you could get something like a Microsoft Surface and use that as both device and control/viewing surface.