I tested Amazon HD before settling with Amazon Unlimited. While testing HD, I noticed that some albums / tracks are listed as UHD but are playing at CD quality 16/44.1khz. Amazon Executive Tech support told me that there are albums (e.g. Nora Jones' "Come Away With Me" album) that is listed as UHD is mis-tagged. Given this fact, I don't think it makes any sense to pay the premium just to see resolutions on the APP that may or may not be accurate. From what I can tell, I can still access all HD and UHD content but do not see the resolution on the Amazon Music APP.
Also, I believe the reference article from audiophilestyle is spot on... The only streamers I am aware of that can stream natively, within its app, are Bluesound/NAD (BLUE OS) and Marantz/Denon (through HEOS APP).
Also, I believe the reference article from audiophilestyle is spot on... The only streamers I am aware of that can stream natively, within its app, are Bluesound/NAD (BLUE OS) and Marantz/Denon (through HEOS APP).