Gents, this discussion has been going on for ages.
I have Spotify Premium and listen to it almost daily via my Bose Quiet Comfort 2 Headphones (No joke! Most of their stuff I wouldn't touch but these are awesome.) As it's just casual listening while I'm making dinner (or some other chore so my hands are free) it's great, but for serious listening I'm betting NoPAspeakers4m is noticing a difference via his system.
Some years ago I did a lot of A /B testing on some of my selected CD's ripped to 320K MP3 versus to FLAC, and even some 24 Bit FLAC files from HD Tracks on a decent sound system. (not headphones) I was contemplating moving to FLAC but I already had a large MP3 collection (about 440 GB => 11,000 Albums / 110,00 Tunes) and a shift would be a major endeavor. (I got into MP3s very early on when Napster was first going. OMG!) My perception was there is a noticeable difference for me between those MP3s and the FLAC files. I even did "blind" tests with my family and friends (and drove them crazy) which mostly corroborated my results.
But the reality is very much individual.
I still have MP3s as my car & iPhone won't natively play FLAC. And they work fine there.
Now for an AVR there is no doubt the best sound source is a Blu-ray with an HD soundtrack. (Atmos or not). Like with MP3s, I have a relatively decent collection of concert DVDs. I was convinced Dolby, or DTS, 5.1 was great. (Eagles => Hell Freezes Over !!) So when Blu-rays came out I decided they were really about the picture quality, which for me with live concerts, was secondary. So (for a change) I wasn't an early adopter.
I ended up buying a Blu-ray player to try 3D Movies on a Samsung TV we bought just for gins. Later, when I was looking to buy a concert DVD, I saw there was only a $5 difference between the Blu-ray and the DVD version. That lead me to reconfigure everything towards HDMI cables to try out the lossless HD soundtracks. (I used to be a big Optical /Coaxial cable fan for AC3.) I again did an A/B comparison with a DVD vs Blu-ray on the same system, with the same concert, (two different players - sorry) and the choice was very clear. I haven't bought a new DVD since.
I know there are some Albums available in Blu-ray Audio but I haven't tried them. I'll wait for you guys to comment on those... I hope this is helpful.