As Sir Quack has pointed out, probably the most cost-effective solution for getting much smoother distribution of deep bass throughout a room to most listening seats, without the severe nulls and peaks common to most rooms used with a single subwoofer, is to use two subwoofers carefully placed.
I'd also point out that a home theater is NOT a recording studio control room, and that setting up panels to absorb the first reflections will considerably reduce the spaciousness of the front main speakers--their ability to image beyond the boundaries of the speakers. Lateral reflections in concert halls (and outdoors) are what cue our ears and brain to the "size" of the front image, and absorbing those first reflections will reduce the apparent width of the musical source.
There may be exceptions if you have an extremely "live" and reflective space with too many bare surfaces, but generally, despite the wrong advice doled out by "room treatment" vendors and manufacturers, you do not want to absorb lateral first reflections from the front speakers.
Axiom Resident Expert