As Ian says, this is data and I personally would take cables as the very last upgrade, if at all.
The audio endpoint is the thing that matters for sound quality and in your system I would buy Meridiians best.
The MC 200 would be an audio endpoint in another less critical zone if needed.
The Qnap would run core and storage and have no effect on sound quality.

You could also look into Roon software as this also streams to Meridian audio endpoints.

Chris

No 18 in the Hall of fame smile I have simple tastes; I am content to settle for the best:
GIK monster bass panels, rear wall. QNAP TVS 471i3. Roon into DSP5200SE via 210/ 218 zone... Explorer 2. Bluesound Pulse 2, Mini & Flex. 596v1, 518, Foxsat HD, Sony BDP, Pioneer 5090, 2 Chromecast's for LRB videos. MS200 to F80 for a Roon zone