If you are considering an 85" TV make sure to check out short throw projectors, they work great. Smaller footprint, bigger picture, more value:
https://www.digitaltrends.com/home-theater/best-short-throw-projectors/
You should get a receiver capable of 7 bed channels, 4 height channels and at least two subs like the new Onkyo, Denon, or Anthem.
Then start with as many speakers as you like and simply add as budget allows, no need to go all in at once. KEY- all speakers should be same brand and ideally same series. I prefer monitor speakers with subs instead or towers but YMMV.