I like very much the Volumio solution and wish you lots of success.
For some reason since a couple of months I am not able to adjust the playback volume using the volume adjustment in the playback screen - I can still adjusted manually by turning the dial on the amplifier but it defeats the purpose specially because it worked perfectly well before.
I tried restarting several times but still does not work. Any suggestions.
Using a Raspberry PI with a Hifiberry amp board but not using the amp only the USB output connected to a Musichall DAC