Hi _scotty_
I have no reason to doubt you have an amazing sounding system, and frankly I'd love to hear it at some point assuming that it's logistically possible and you're up for company.
You write very intelligently and informatively. And you've also gotten Charles to write how grate your system sounds
You're also posting links from people with phds and thesis data on the subject, so I'm personally in no position to question that type of authority.
To your point about the subtleties of the sub woofer so as to not draw unnecessary attention to itself , that too is very very true.
But this is the reason that I'm stating that it's not so simple to implement. I'm sure you'll agree you have two basic components to the matter ( some other things too but the two basic major ones) which are your crossover frequency (where the sub begins to kick in) and the output level setting.
The sub shouldn't be noticable (meaning shouldn't draw unnecessary attention to itself) when it isn't needed, meaning it isn't being called for by the source content of the recording.
On the other hand, setting the subs in such a subtle manner has to be balanced with the fact that there is plenty of music content that demands the use of subs in all of its glorious splendor.
For example, play (assuming you have access to this music) mickey hart - The Gates of Dafos - vinyl remaster 1644.
When played at a proper decibel level , say 90 DB or above, your subs should essentially emit such power, that it now gives you an opportunity to check if there are any unwanted resonances in the room. In other words, the bass and subbass is anything but subtle. The sound would certainly be penetrating walls.
Now what I don't know (have never tried it) is if using four subs in total (two in the rear and two in the front) means that the two that are in the rear and out of phase (as you suggested) firing towards the front subs is going to result in an accurate representation of how that particular song track should sound.
I suppose this is one of those cases where life is not being in the "know", it's being in the "mystery".
Best.
Hal