Now... back to my original USB query...
Simple answers to your questions:
- The USB audio driver built into Windows sends audio to the Audioengine D2. No additional driver needed.
- To JRiver MC, the D2 DAC looks like any other DAC.
- Your son will want a way to select and play music in the theatre room. You can do that with a laptop PC running MC but a tablet or smartphone is more convenient. He can choose between JRemote, Gizmo, WebGizmo (which runs in abrowser) or WebRemote (which also runs in a browser.) In he is using MC22, he can use the new Panel software. All of those approaches depend on your son's having a WiFi or wired Lan network in his home.
The D2 is simple to install and use. You can connect it to a PC via USB or SPDIF. The main concern is that if you have a lot of wireless activity in the home, the D2 may not be able to transmit audio reliably. I tried a D2 and found that there was too much wireless activity in my home.
Other people have suggested more complicated alternatives. If your son likes the D2 approach, it is a reasonable choice.