custom streamer

[LTTRony]

I already have 3 rotel a-12 stereo amp. The original purpose for these amps has been cancelled, and i want to use them to make a multi-room audio system.

 

I plant to use a windows based server to store the music and connect to this pc all the 3 amps via USB, so I can select every amp as a different sound card to make the sound go to my selected room, selecting what sound card i want to use. 

I decide to use USB because of the distance between the pc and the rooms, usb wire is cheaper, noise-free, I can take advantage of the Ethernet infrastructure and the quality of the integrated DAC  in the rotel is much better than any on a PC.

My first thought was to use one of this: https://www.bluesound.com/products/node/ (or any similar streamer) attached to each amp, but it is quite expensive and I have much of my collection stored and shared via DLNA.

 

And the problem is, how can I control this thing in a intuitive phone/tablet app? Is there any app to control a pc as media player from the phone? Can you give me another approach to achieve the multi-room project, maybe attaching 3 raspberry to each amp via usb?