Why the fascination with subwoofers?

@atmasphere 

I'd give it a shot. I don't use the Swarm but if I had it to do over that's the route I'd likely take. Duke is working on a sub system for me though- one that is integrated into a coffee table. It will be used to break up the standing wave in my room.

Interestingly, my additional two subs would go disguised as coffee tables as well. 

Ok, so you don't use swarm, but I take you are replicating the concept: distributed bass array playing a mono signal. Is the goal to minimize SPL variations at different seating locations? Or to optimize at the prime seat?
How did you determined you needed to break down a standing wave?

Regards

Ok, so you don't use swarm, but I take you are replicating the concept: distributed bass array playing a mono signal. Is the goal to minimize SPL variations at different seating locations? Or to optimize at the prime seat?
How did you determined you needed to break down a standing wave?

The goal is uniform bass response in a greater portion of the room including the listening positions. I've done lots of setups over the decades as I've been doing audio shows since the late 1980s; so the answer to your third question is 'experience'. Standing waves are a common problem in a lot of rooms. One time we used an Accuphase room correction device but quickly learned that it can't do anything about a standing wave. If one is present, you can put as much power into it as you like and at the null point the bass still won't be right.

So the elegant approach is to use a distributed bass array system like the Swarm, which is the best example out there.

Do you have to play a mono (i.e., summed) signal from all the subs or would there be value to trying the front subs in stereo and the rear subs or one rear sub in mono to better deal with standing waves?

@atmasphere 
Ralph: if I'm taking measurements and measure a deep valley within the subwoofer frequency, would that be pointing to a standing wave?

@mitch2 
While many records have very similar low bass recording on both channels, to be certain it works you should play a summed up mono signal to achieve this.

mitch2,

     It was mentioned earlier that humans are unable to perceive true stereo in the bass frequencies below about 80 Hz.  Even if you were an exception, there's the problem that there's virtually zero musical content recorded with discrete L/R bass signals.  I'm aware of none in cd or lp format.
     I run my 4 subs in mono mode because of this.  As I've stated before, however, I do perceive the bass as stereo in my system on well recorded cds and 24 bit/96 Khz FLAC files even though I believe the bass is summed into a mono signal.  By stereo bass, I mean I perceive the bass as originating from the proper position within the sound stage illusion.  For example, the kick drum dead center and the upright bass a few feet forward and a few feet left of the kick drum. 
     I can only explain this by assuming that the higher harmonics or overtones of the deep bass fundamental notes's frequencies extend beyond 80 Hz and are being reproduced by my main speakers, giving my brain the clues it requires to associate the higher directional harmonic frequencies with the much deeper and non-directional fundamental frequencies reproduced by my bass system and determine the specific locations of the bass instruments.
    In your situation, since there are no recordings with discrete L/R bass channels, locating a sub in the middle of your back wall and running them all in mono would give you smoother bass that you'll perceive as stereo bass.  Adding 2 more subs, running all 4 subs in mono and positioning them where they sound the best to you will provide the smoothest, most natural, most dynamic and effortless bass that you'll perceive as stereo bass.  I'm almost certain it'll provide the best bass response you've ever experienced and it will provide sota bass response throughout your entire room, not just at a single sweet spot. 
     I can share a best practices method to optimally locate each of your 4 subs if you're interested.

Tim