I wouldn't wory about Dobly Atmos yet. There isn't many sources out there. Give it 3-5 years and then buy your next A/V receiever smart.
Thanks for the comments that followed on Atmos, it makes much more sense the way you explained it than most web sites I saw.
I'm actually leaning toward just doing nothing for a while, at least in the biggest room, as it will be more of a game room than anything else. The more I think about it, there's no "right" way to arrange speakers and sound in that room, as people will be moving around (large pool table in the middle) and so calibrating sound for any given spot makes it pretty wrong for all the other places someone may be. In fact, I think that using stereo as opposed to surround sound would probably work better, keeping the "center" available near the back of the room.
I'll wait and see how often I even have the TV on when people are visiting.
I think I'm good in the "TV Room" aka den, with my old AV amp, now that I ran wires.
The one I still need to fix is my office. I spend most of my alone time there, and probably 80% of the time have the TV on. The current sound is adequate, but the den's sound is SO much better I think I will do something there. And wireless there would be really good just due to the way the roof falls (and frankly because summer is just starting and I hate going into a SW Florida attic in summer).
I also think for that room I want "fake" front speakers, i.e. a sound bar for the left/center/front, not discrete speakers, as I have no where to mount discrete left/right other than far corners and that's bad acoustically I think.
I'm thinking of the vizio SB36512-F6
It has discrete woofer and surround speakers that are wireless, it claims atmos and I am probably paying a bit more for it even if it won't get used, but maybe it will do something. It seems well rated generally. And it's cheap enough that if in a few years there are better alternatives I will not feel awful if I give it away to my kid or similar.
Then I'll wait and see how much I miss better audio in the big room, and see if I ever really want an upgrade in the TV room, and spend bigger money only (a) later when the standards might settle a bit, and ( if I need to.