Distributed Bass Array configuration

That is a great quote and relevant Tim, and thanks for saving me the time of reading the whole interview. Your last comment is one of the clues that helped convince me DBA was the way to go.   
The only times we experience truly low bass in normal life is in very large to wide open spaces. For me it was always one of the coolest parts of going to a rock concert, that vast space feeling of bottomless bass. This was always missing, particularly in orchestral works, because even if it is on the recording the system simply cannot reproduce it at home. Even if the system response measurements look good still there is always the room that ruins this.   

I'm sure you know where I'm going with this. One of the more surprising things with a DBA is the enhanced feeling of envelopment. People have commented on it with my system. It is very deceptive. First, because no sound whatsoever appears to be coming from the subs at all. But also because the low bass that triggers this feeling isn't even heard or sensed as bass at all. It has no pitch, nor location. It has no attack or slam, no harmonic, no tone at all. Yet somehow it creates this ineffable feeling of being in a huge space.  

Nothing else does this, at least not to this extent, and I have heard some pretty awesome gear in some damn fine rooms. Yours as I recall are one per corner. Another one has this plus one way up high near the ceiling. Mine are along 3 of the 4 walls. It seems to work well almost regardless of how the subs are laid out.

Please correct me if any of my comments here are incorrect as I don't claim to have any expertise. I do believe you are misinterpreting the  "term" - "stereo subwoofers". It is a "term" not a sonic phenomena or an implementation in any recording process . I do believe it was originally  meant as the description of using 2 subs on receiver/pre amp as 2 separate channels so not to not to be confused with 2 sub outputs running parallel. Although this is a 2 channel discussion listening subject  I do believe the whole concept began with surround sound and then was deemed profitable for 2 channel listening. So, when a surround sound mix is configured for a movie the "LFE" channel is single and mono ( as is every channel / speaker ), it does not have a left sub mix and a right sub mix, much less a 4 sub mix, it is a single signal. Then the receiver through it's processor separates it to a left channel and a right channel so the mic calibration processing then allows for different volume levels to be "matched" at the listener position. Now recent implementations of Audyssey and definitely Dirac LIve may incorporate separate phase shift and delay but it all comes from a single mono signal being manipulated to create a "means to an end".
Again correct me but isn't "stereo" in itself just taking a recording from multiple "mono" microphones and then an engineer manipulating all the separate mic channels into a "stereo mix" in an effort to create a "perceivable" soundstage again as a means to an end ? I think we should use the term multiple.
I listen to Paul McGowen on Youtube ( maybe the meaning of stereo subs is a good question to send in ) and consider him quite informative but don't take all he says as undeniable truth. Actually, I believe he has mentioned that the owner of Audioquest is a friend of his and I heard that guy the other day on YouTube say that power regenerators are useless ( and a great amount of Paul's expertise and companies monetary value is based on that very component ) so I guess even his friend and also an "expert" doesn't agree with him. I might mention that his company is often criticized as not legit in the premises that their products are based on . So who are the experts? 
But let me conclude in complete agreeance that we can't discern the location of the lowest frequencies, it's just a fact. Our ears/brain don't work that way for a reason. In real world circumstances there is no practical use for "hearing" those frequencies. One main component of hearing and discerning placement is to realize where danger may be coming from and if your in danger from something creating sub harmonic frequencies it's probably an earthquake and you ain't getting away from that.

My B&W older 803's, as well as my stacked DM24's sat on top of my stereo subs.  I measured the woofers on all speakers and phase aligned them.  I know that it is taught that sub-wooferage is non-directional, but tell that to my ex-laundry room bass trap, electronics room when the door is left open.

Any Sub Woofer set @ 80 HZ Crossover will interact with every Good Hi Fi Speaker's Bass Output.  This should be avoided.

Setting @ 60 Hz or so should minimize interference & blend in better.

With Sub Bass, a Crossover of 40 Hz or so would be appropriate.

1Hz XO resolution on subs and mains is nice.
Sub and mains may not necessarily crossover at the same frequency and more than probably at different slopes.

I often imagine that DBA is a lot like what happened in a mastering lab in the LP days: After listening to glorious 2 channel bottom end in the studio, it got sucked down to mono below 40Hz. And these guys recommend 80Hz w no XO on the mains. Surely you jest?