It's not a sound system if it lacks Dolby Atmos? Atmos is cool and all, but unless you've got a room well set up for it, it's not adding much. Even my current 7.1 is too much for my room, and before I drop money on Atmos, I'd want to shell out way more on accoustic treatments.
Also, if the movie is any good, I quickly don't notice the format. I'm rewatching LotR since my daughter is now old enough to enjoy them. My copies are DVDs. I've never felt the need to replace the DVDs because the movies are solid enough that DVD quality is fine, even on a 4K 65" screen.
Planet Earth II definitely benefits from 4K HDR, but then I'm not settling for streaming level compression, since I'm basically looking for Nat Geo level photography in every frame, so I'd buy the UHD BluRay.