Amazon Music is a little more difficult to stream than some of the other services. They don't share the API and don't support Linux like some of the others.
An Amazon Echo Link is one solution. it does have cozx and toslink out to connect to your dac or RCA out to bypass it
Personally I use an inexpensive i5 Fanless PC and USB to my DAC. There are lots of RemotePC aps to control the computer from your phone. This gave me the highest resolution for not much more than a Link