best streamer for Amazon Music HD

That's great amosm.  Are you happy with the functionality of Amazon on BluOS?  How does it work with playlists?  Can you add songs to Amazon playlists?  Or do you create a playlist on BluOS?  I already have a lot of playlists and songs added on Amazon app, wondering if I BluOS will recognize or if I can import them to BluOS.  Generally not sure how BluOS interacts with native Amazon app features.

I'm also an AmazonUHD fan. It coincides well with typical Amazon account, add-on to Prime membership. Cancelled Tidal when AmazonUHD launched.

Have both Denon AVRX6400H (HT system) and NAD C388 w/BluOS2i (2ch system). Both AmazonUHD capable, NAD is also Tidal native-MQA capable.

They both work splendidly over Wifi for me using mesh-capable Asus routers (x3 for coverage of 1 acre). Funtioning very similarly, using PC/Android app and Alexa (voice control). They will also receive Bluetooth, but aptX won't provide same sound quality (limits of BT bandwidth) and limits of BT range (if you step away). If using HEOS or BluOS, they will keep playing (if you leave - to get gas for the mower) and control range is limited by Wifi connection (control device must be on same network). Think of them as (because they are) Wifi connected remote controls that don't stop playing just because the remote left (to get gas). HEOS works easier with Alexa - just say, "Alexa, play modern country in the basement." (wife), and Denon turns on, TV turns on, GoldenEar Tritons come to life with UltraHD (FLAC) quality Tim McGraw - happy wife. BluOS's Alexa integration isn't done as well (they don't have the deep pockets of Sound United for app development folk). BluOS requires, "Alexa, tell Bluevoice to...". If you've used voice command tech, you already know fewer words is always better to avoid confusing Alexa.

HEOS also displays album art and stream quality onscreen (with TV connected), which is very nicely done with album art repeated blurred in the background layer - which color-matches the display for each track to terrific effect (again, thank you Sound United). NAD C388 doesn't have HDMI out, and nether does Node2i. There is an HDMI MDC module for NAD, but I cannot find confirmation that album art is displayed, so I think it is not.

I don't have experience with Marantz, but same tech is shared between Denon/Marantz twins. The downside of Denon/Marantz... class AB amps, and they run HOT. I added an ACinfinity rack fan to keep AVR-X6400H from melting the Xbox1S sitting on top of it; or, you could use it to make popcorn halfway through a movie. I also have a 12ch ATI class AB amp, and it doesn't get hot (and also has no internal cooling), so it's not the amp class or multiple channels - Denon/Marantz just run hot. On the other (un-burnt) hand, NAD C388 class D (Hypex UcD) runs completely cold while delivering 400wpc into 2ohms - no cooling fan req'd (+1 for class D).

For usability and Amazon UltraHD streaming integration, I recommend Denon/Marantz - don't place anything on top or let small children play around it with Crayons. BlueOS works equally as well, without on-screen album art display and wonky voice control. Both deliver great sound quality and PC/Android app control. Another cool feature is if I startup BluOS on my laptop, start some music, turn off the laptop (music still playing), then start BluOS app on the Android tablet, it shows the same as PC app, and just picks up control seamlessly - same with Android phone. You can have them all running BluOS at the same time - change song on one device, and watch it change on the others. Quite seamless across control devices!

Answering your question about creating Amazon playlists in BluOS app.

You can access Amazon playlists - that were created in Amazon Music.
You cannot create/delete or modify Amazon playlists from within BluOS app.

Here's what I do... If I want to create/delete/modify an Amazon playlist, open Amazon Music app and make the change there. Go back to BluOS, and you will see the change has been made.
Here is a typical example: I'm using BluOS to listen to an Amazon station "Modern Folk", and hear a track that I want to add to a playlist. Open Amazon Music app, search for the track, add it to the Amazon playlist. Bring up the playlist in BluOS, and the track will be there.
Is this ideal? No, but it works.

I found the topic thread during my regular check for a good streamer for Amazon Music HD. So I couldn’t resist to jump in.

I am a fun of Amazon Music HD, mainly due to extensive music content HD/UHD.

My experience with BluOS + Amazon HD was disappointing. Check here:
https://support1.bluesound.com/hc/en-us/community/posts/360037587193-Amazon-music-support-roadmap. I would be interested if Denon app, HEOS, can manage big (> 10000 songs) list of Albums/Artists, here I mean browsing and filtering.

I have some hopes from Sonos Port. In June Sonos will switch to new OS and new App and it will support high resolutions. And Sonos app is one of the best.