My personal take is that I don't care about 4K or 8K or anything beyond 1080p.
I can't even tell a significant improvement between 720p vs 1080p from 10 FT away.
I don't think you can truly benefit from 4K if your TV screen is smaller than 80" and you sit 10 FT away.
I might be able to tell the difference between 1080p vs 4K if my screen were 300" wide.
But if you think you will be able to benefit from 4K over 1080p, then go for HCDP 2.2. The Denon S910W is 2.2. But because it's new, lowest price will probably be about $500.