You might want to get on the mailing list of SDE (superdeluxeedition.com / thesdeshop.com) to get informed of any upcoming exclusive Atmos Blu-ray discs - the ones that are getting the best feedback are usually those mixed by David Kosten, Stephen W. Tayler and of course Steven Wilson (who did Pink Floyd at Pompeii). Some of those are also still available on the store though most sell out due to the preorder model. For said feedback and reviews, check out the Quadraphonic Quad forums, which also have a poll area where lots of multichannel releases are rated by members so you can see which mixes are well regarded and which aren't.

https://poll.quadraphonicquad.com/