You keep wanting the best, but then you cut down your budget.With that being said is the Nvidia capable of multiple streams areound the home? What are the best options to ensure the whole family can enjoy content without lag or considerable buffering
Build a decent unRAID server (i5+ or Ryzen 5+) and get Shields for each device. Run Plex Server as a Docker on the unRAID server and direct play to each client Shield. That's pretty good and expandable. If that cost is too high then drop down each client on the secondary TVs. That'll make the server work harder. Drop the QNAP idea.