The trick is to have the space to set them up and a deep knowledge of the physics.
Hmmmm, so in your opinion the layman shouldn’t use a subwoofer without engaging a physicist? I have 0 problems with your system, I think it is excellent. Your room is excellent. Your advice makes me wonder. I don’t think you need to be a physicist to set up a subwoofer. I stand by my post above:
A) Place your sub (s) according to the manufacturers recommendations.
B) Place bass traps from floor to ceiling in the corners.
C) Run a dsp program like DIRAC, Audyssey, ARC,Mini-DSP, DSPeaker, etc.
Leave the physics to the sub designers and DSP programmers.
You don’t have to believe me, a simple measurement will confirm. Using two subs should be much better bass management than one. If you have the space for four, great, but that is a nice to have, not a need to have.