Subwoofers. Yes, plural.
You have a huge volume to pressurize. Your "room" opens up into the entire first floor.
IMHO you will need, at the minimum, a pair of Hsu VTF-3 Mk V subwoofers placed near-field in order to have any bass. You will probably require some if the 18" monster subwoofers from JTR, PowerSound Audio, or Rhythmik. (Yes, I am fully aware of DSS and Funk with their 24" offerings. Same with DIY subs).
Basement 5.1.4: Anthem MRX 720, Monoprice 2-channel amp, Paradigm Prestige 85F/55C/15B. PSB Alpha A1/P3 for Atmos HSU STF-2, ATV4K, XBox OneS, Harmony Ultimate, Samsung 65" Q7D.
Living room: Yamaha YSP-6000 with 10" Yamaha sub, ATV3, Harmony Ultimate, 55" Insignia 1080P.