Volume on my system is too low with streaming! Help!

I am looking for assistance with an issue I have been trying to research online to no avail. I am a big fan of "Surround Audio" (5.1, ATMOS, etc) and have been purchasing music in these formats the last 20 years or so. Unfortunately, finding actual copies of my favorite artists have been difficut. After just getting in Pink Floyd's DSOM on Blu-Ray with ATMOS I had an incredible listening session. I should note, this is the 4th Dolby ATMOS BluRay I own with the others being 2 Beatles (Abbey Road & Let it Be) and Rush's "Moving Pictures". I had recently purchased the CD remaster of The Beatle's "Revolver" but was dissapointed as I thought this would come with an ATMOS version BUT according to their site it is for "download only". Note, I STLL can't find it anywhere. I have also been noticing there are other artists that are streaming music in ATMOS that are not available in a physical media. So yesterday, I decided to take "the plunge" and give Amazon Music HD a 90 trial run. After getting it downloaded on to my FireCube (Gen 2) I found a Dolby ATMOS playlist. I saw the Beatles, Floyd and many other artists so was pretty excited. However, when I went to play these tracks the volume was so low I had to crank the master volume from about 48db (my usual spot +/-) to 70db to get the same apparent loudness. Not only that, but I played Pink Floyd's "Money" and the cash register sound effects were coming from different speakers than I hear on the BluRay version. Similar differences were heard on other tracks from DSOM. BTW: the BluRay is not only a different ATMOS mix but light years better sounding.

This is the equipment I am using:

* Marantz AV7706 preamp * Separate amps for 5 speakers (L, C, R and LR/RR) * Marantz 6 channel amp for Ceiling FL/FR, ceiling RL/RR and two "surround" speakers situated to the immediate L & R from the listening position. The BluRay audio source is from an Oppo BluRay player via HDMI to the Marantz preamp where DSP is done. The streaming is also via HDMI from the Amazon FireCube Gen 2.

I should point out I have the audio leveling set to "off" in the FireCube, have the audio set to "best possible" and use the "Direct Input" on the Marantz so it is not "manipulating" the signal a second time. My first though was the HAS to be something going on with the output signal but have used this FireCube for TV's and movies for over a year now with no issue. I just have never streamed music. I went into the "Advanced Audio" screen and it shows all the audio confirming "yes" to the various outputs, ATMOS included. So my experience was, "wow it's cool to be able to try out these different artists" BUT the sound quality was not what I expected. I guess I'd be "ok" if it was just the volume issue but the fact the mixes were so different than their BluRay audio counterparts. I just refuse to believe they would mix it one way in ATMOS for home and another way in ATMOS for streaming - that just doesn't make sense...

Anyway, sorry for the LONG diatribe but I am new to the whole streaming thing and don't know if others have encountered the same. Is it something I'm doing wrong/overlooking in the settings? Is this what I should expect because of how they encode it? Unfortunately, the handwriting is on the wall and owning physical discs is going to get harder and harder - or be included only as part of these super-costly box sets. if I want to hear the new Def Leppard, Blake Shelton or tons of others in ATMOS streaming appears to be my only option (sadly)...