Seems to me you are listening in a nearfield environment much like I do in a smaller 16x21x10 room with two large openings to other areas.
Are your current speakers failing in some way in that location in a nearfield environment? Or, are you looking for a bit 'more volume or substance' for the entire large space when listening in the background. Larger might be better then.
I'd sure suggest a 4-sub Dist Bass Array to help the space's bass and boost the extreme low end. More details please. It's an interesting question.