Experience with stacked subwoofers?

Fair enough. Good luck. I hope you accomplish what you want to.

So far I have four of my six dialed in very nicely, for classical, jazz, classic rock that I listen to on vinyl. I'm very satisfied and looking forward to getting the last pair from my dealer (within a few days I hope).

Oops. In my comment about the post above by @simonmoon regarding the GR Research/Rythmik Audio OB/Dipole Sub, I neglected to say that AudiogoN member jaytor includes pics of his stacks of the 2-woofer model of the sub in his virtual system. Four 12" servo-feedback ob/dipole woofers per side = awesome!

@emergingsoul 

You sound like you have no practical experience with the use of multiple subs and are merely parroting outdated information.

Adding a distributed bass array consisting of four subs (not stacked, but distributed throughout my listening space) to my two channel setup resulted in the single biggest improvement to it's overall sound quality. 

The haters just need to hear a properly setup REL line array. That usually dampens the conspiracy theories about marketing and other deceptions, that lack any evidence.