Need some nearfield permanent build options
First, a bit about me, my space and system:
I own a custom cabinet shop and was a general contractor before that so I can build anything you throw at me. My room is 19x15x10 but I only use 12.5' of the 19' width for my home theater (see attached pic). There is 41" high millwork behind the sofa but is otherwise open to the rest of the 4800sf house. My system consists of a Marantz SR7013 head unit with Polk Signatures all around. S60 fronts, s15 surrounds, S30 center, MC80 heights, HTS12 subs. I also have a LSiM 706c that I might swap in for the center, but haven't A/B'd them yet. My use of the space is 50%TV, 30% movies, 20% music but the system really doesn't get used for general TV watching, which is typically at relatively low volumes. Actual system use therefore is closer to 60% Movies and 40% music, but even then I often go 2 channel with music. Current speaker placements aren't ideal but I had a beam and a post to deal with so it is what it is and with calibration, it works.
What I want:
Due to cost and WAF, I can't have massive subs visible so the HTS12 pair will have to do. Don't get me wrong, they are very effective at drawing us into a movie and are surprisingly good from the mid 20's and up. They vibrate the house, including dishes in the back wall of the kitchen 50' away. What they don't provide is that elusive chest punch. I also don't know what I'm missing under 20hz (ignorance is bliss?)
How to get (hopefully) what I want:
I have 3 boxes behind my sofa that I can repurpose (see hashed area in attached pic). Each box has internal dimensions of 31.75x31x12 giving a volume of 6.8cuft for each. I won't be using those boxes (melamine). I will pull out 1,2 or all 3 and build a proper braced enclosure for whatever I need. The boxes are attached to the floor on a kick as well as to the post on the right and the wall to the left. I may need decoupling solutions. My basement is currently being finished so I'm pressed to bring whatever wiring is needed behind my sofa while the ceiling below is open. I don't really have a set budget, but whatever equipment I end up with should take the current setup in consideration. I don't know much, if anything about DIY builds to achieve my goal. This is where you bright minds come in.
Marantz SR7013, Polk Signature S60s/S30/S15s/HTS12s, Polk MC80 (x4), AC Infinity T9/S9, AAB4 HTPC,...still to come - Panasonic DP-UB820K, 82" 4K QLED or eqv.