Thanks for the suggestions all. I ended up getting a Fire TV stick (the most recent one) and going in through my HDTV, taking optical out to my current DAC/processor, mainly for Spotify Connect (I already have an Apple TV which I use for other stuff as well).
For $40, it's a decent solution for now. Can't really tell if it's doing 320 Khz streaming through the Firestick, but it sounds good to me, a bit better than Apple Music through the Apple TV, hooked up the same way.
I might be getting a new processor / DAC in a month or so, which does HDMI in, so it will be interesting to see if it help getting the TV out of the chain.
The Raspberry PI and Bluesound Node solutions sound cool, maybe I'll give the PI a try in the future.