Eh hem!...Subwoofers... What do ya know?

2 subs are better in that you have more power, and more driver pushing air.

So absolute terms, sure, you can increase output by 3 dB with lower distortion.
But if you place the subs symmetrically, I would imagine that you end up reinforcing the same mode and anti-modes. Maybe some one has a better idea?

As far as I know, you place the first sub as well as you can, and then place the second sub so that it fills in any nulls.

Is this not how the cool kids do it today?

A very interesting, and appealing discussion. I've never heard a subwoofer swarm demo--perhaps a demo in Florida in February (he said, hopefully)? Two questions please:
1) From what I read here, it seems like multiple  in-wall subwoofers would be a good swarm solution...yes/no?
2) Millercarbon: what subwoofers do you use for 16ohms?

Best wishes from Atlanta, where Christmas buyers are also swarming...

@erik_squires  placement in terms of nulls makes perfect sense.  I will read more into that

Whoever is interested in subwoofers for his audiphile setup shall strongly consider "The Swarm" subwoofer system from Audiokinesis (or some simmilar setup of 3-4 small subwoofers). I'm using this kind of system (4 subwoofers) with Soundlab electrostatic speakers and I enjoy it so much. Previously I've used a single REL subwoofer with Quad speakers but the marriage was not realy good. 

1) From what I read here, it seems like multiple in-wall subwoofers would be a good swarm solution...yes/no?

Yuck! The beauty of DBA is quantity matters more than quality. But, come on! A man's got to know his limitations.

2) Millercarbon: what subwoofers do you use for 16ohms?

Morel 10", which are a nominal 8 ohms each. With four subs and two amps you can get a total 4, 8 or 16 ohms simply by changing the way they are connected to the amp(s).