Plex would be a good option if your QNAP has an x86 processor, else you may not have enough processing power. I run Plex server on my QNAP and I store all of my music (500+ albums) and movies on it. With that said, no matter what server you end up going with, the WiiM app does not have the best interface and playlists are local to the device (phone, tablet) that you are using, thus you'll see a lot of suggestions to use apps such as BubbleUPnP or Plexamp. I did initially use the WiiM App, but have now switched to Plexamp and cast via Chromecast. It works great for my needs, but I'm also bought into the Plex ecosystem.