Many people talk about using ROON to manage the streaming as a way to not lose quality. People have mentioned it for Amazon HD.
But on ROON's website they state this:
Roon is B.Y.O.M. (bring your own music). Roon does not come with any music but has great support for your digital media files. Roon also supports TIDAL and Qobuz. Just log in with your TIDAL or Qobuz account in Roon and all your music will automatically get synced in Roon. Roon does not support Spotify, Apple Music, Deezer, Amazon HD Music, or YouTube Music.
So, how does that affect using Amazon HD Music with an x3700h?
Couple of things about Roon:
-It doesn't work with Amazon HD, just Tidal and Qobuz
-You can use Roon to work with Denon and Marantz receivers as they work with Apple's Airplay 2. However, note they won't do anything over CD quality (no hi res if that is of interest)
-You don't need Roon to "not loose quality". I believe the built in streaming app heos supports streaming services that do hi res audio. Not completely sure which ones as I don't use them
-Roon costs $119 per year or $699 for lifetime. You need to run the server software (included with subscription).
-There are a ton of great things in Roon... very slick looking interface, very good ways to discover new music, multi zone support, integration of your local music and Tidal/Qobuz, and their fantasic dsp/eq. It isn't for everyone, but for many it is worth it. I really like it.