You have received lot of detailed responses from members.. Here are my inputs..
GIven it is a dedicated room, i would suggest a 9.2 AVR, and with your room size you can do 7.1.2 (or) 5.1.4 Atmos set-up, depending on which side of the room you intend to use..
Pioneer LX 303 / Onkyo TX-RZ 730 are some more choices to consider..
Given that prime, netflix offer multi-channel content for movies and web-series, others would catch up soon, you should consider a 9.1 set-up than 7.1..
Let the subwoofer do the majority of the lows and you can settle for BS, which should be adequate for your room size.. Consider skipping FS and consider dual subs as it is a dedicated room..