Why the fascination with subwoofers?

I am a former AudioKinesis owner and really respect Duke's work. His Swarm is a great system. I took a similar path as I wanted smaller drivers and boxes. I use 8" drivers in 0.4 cu. ft. sealed boxes. The four boxes sit at various spots in the room. I use a Beveridge RM-3 active crossover with LP and HP boards cut at 100 Hz, Linkwitz-Riley 4th order 24 dB slope. Amplifiers for above 100 Hz are either Atma-Sphere or Music Reference, the bottom a vintage Luxman. I use this set up with my ESLs and box speakers and all I can say is I wish I did this a lot sooner. I can't see going back.

@brskie,
I own the non-CT Treos, and have 2 2wq subs. I am very happy with the combo. So much so, I will probably get the new Sub 3's when I sell the 2w's.
If it were me, first I would ask Johnny.
Barring that, I would think getting 2 Sub 3's with the Treo's might possibly be a smidge better than the Quatro's(as you can distribute the bass within the room)- Only if you have limited room/placement options-which is my problem.
The Treo's are a tad smaller than the Quatro's and I can place them easier in my cluttered LR/DR.
As far as amps go, the Pass should be a nice match. I have no experience with AR.
One thing I would offer is that Vandy's like zero feedback amps.
I use Ayre and Atma-Sphere.
Bob

@yogiboy ,
Vandies don't 'need' subs, but having them really fleshes things out, subtle but noticeable. Quatro's have built in subs with equalizer.
B

If you can hear the sub, then it's too loud.  A good friend of mine always has his up a bit, and he complains that he cannot hear mine.... but you sure miss it if I turn it OFF.  In my studio I run stereo 15" subs... they make great monitor stands, but they do not call attention to themselves unless the music demands.   

Hello hifidream,

     Congratulations on creating your own custom distributed bass array system for your Magnepan20.1 speakers.  I know the 20.1s have very good bass performance in stock form with 2 large planar-magnetic bass panels in each speaker that all output down to 25 Hz.  Not full extension to 20 Hz like many good subs but close and very respectable.
     Counting each pair of bass panels as a sub,  I would suggest you're actually using a total of 6 subs in your room/system.  While 2 aren't outputting bass that's fully extended, they're both outputting the exceptionally fast, articulate and smooth bass provided by planar-magnetic panels down to a deep bass level of 25 Hz.  

      Since we've both experienced the amazing seamless integration with even fast planar-magnetic panel speakers (whether mid-level models like mine or top of the line models like yours) and the high quality bass produced using  4-sub dba systems, I think it's safe to assume you'd agree that the dba concept works exceptionally well.

Tim