Why not 2 storage spaces, and keep all the headroom for the room? Some small soffits could push the end walls back
further, at the expense of storage.
One of those walls could simply be an acoustically transparent wall and AT screen. Even be retrofitted easily, down the road, as a
projection upgrade possibility. A 77" HDR tv will have a better picture, but an AT screen and pj with but 3 seats, means that 77"
might be as little as a quarter the viewing real estate. The AT screen also hides speakers/subs/bass trapping, and the soffits could
represent cable runs to a back wall, in-wall av rack.
The extra volume of a larger space is also going to offer smoother audio response. I personally would looking at just how little
storage I can get away with, to better the theater space.