Study a lot more about DBA. All the "one sub" people are about 20 years behind the times. Instead of learning the physics and psychoacoustics that makes a DBA work so well they persist in trying to fight physics with DSP and tube traps. The principles that make a DBA work so well are the same as will get you the most possible from fewer subs. Namely, asymmetrical placement.
Another one the old school laggards miss, a great deal of the boom and other acoustic problems is due to speakers being coupled to the floor. Use effective isolation like Nobsound springs or even better Townshend Podiums and you will be shocked how much of this "room acoustics" problem goes away.
Basically the choice you have is do you want to be the kind of audiophile who does what works, or the kind who does what everyone else is doing? Logically, every time something better comes along nobody will be doing it. You will remain mired in the past. Think about it.