best streamer for Amazon Music HD

First, I must state that my AV7703 is hardwired with Cat 6 LAN cable routed from downstairs to upstairs Media Room through my garage and attic. That is a run of at least 250 ft. There is zero latency at this length of run.  As for the HEOS app functionality, I am satisfied with the options. I am outputting the video to a Samsung 1080p computer monitor using HDMI via DVD i.  The album cover art is in color and is brilliant with the artists name and song name. The options available are Loop, Play last track, Pause and Play next track. There is a button selection for Queue. It displays the time played and shows time left to play. Furthermore, and the app does NOT have this feature, the track display shows the codec and the sampling freq and the bit-rate, i.e. FLAC / 44.1kHz / 24 bit. 
I am still comparing the two platforms, HEOS vs BLUOS on a Node2i; but, right now, I like the HEOS enough to not be distracted. 

BTW, in case it was not obvious, I am controlling all of the HEOS functionality with my Marantz remote control, not a glitchy iPhone. However, when I pull up HEOS on my phone it is mimicking what my Marantz is doing. Advantages of this is I can be downstairs and still have control over my HEOS. Just realized also that I can pull up the Amazon app on my phone and select my AV7703 as my endpoint and use the functionality of the Amazon app to control it all. 

I have a Blue Sound Node2i which I use for the interface through its Blue OS. I am using the external DAC on the Marantz SA8005 through the optical cable. I tired this connection with Tidal and Spotify before, and I was very disappointed with both of them. Tidal is better but It lacks something somehow. I then moved to Amazon Music HD. This set up is perfect in anyway. The instruments are much more clearer and the bass is defined better. You can use the internal DAC on the Node2i but I find it inferior. 

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!