Just read this thread, nice job on all counts.
If you're still interested in the tactile element, ... place the rear sub near-field, evenly behind you, and with a Behringer DCX2496 (or equiv) carefully time align front and rear sub separately, then EQ globally. Also, by tweaking low pass of each, the acoustic summation varies, and with all these tools, you can retain the bass "upfront", yet elicit the tactile immediacy you're after.
As you know, the near-field placement yields a by product of FR smoothing, because you're getting more sub, less room,..relatively speaking (just like close mic measuring). This fills in most all modal nulls, yet with judicious time alignment (and careful low pass adjustments), you weave the LF properly into the mains, yet you gain back the tactile component you're missing from the concrete slab.
Anyway, just a thought,...I'm guessing you've tossed all this around many times.
Nice job documenting, I'd like to see more and better FR graphs, but that's really getting picky in an otherwise well executed build.
Just a thought
(remember, when fine tuning in the time and freq domain, keep going back thru the steps, as each parameter affects the acoustic summation perhaps subtly and differently, so going thru again and again is a must, IMO, time align separately, EQ globally,..with exception of low passing)