subwoofer question......what size sub ?

The Dual core will function as the sub crossover and volume control as the 8033 will not . I have both units . I use the dual core for my stereo distributed bass system .

This is good information about these two models. I'll go get the details.
Thanks,
Kenny

Vandersteen Sub 3 coming soon
advantages
• no DSP processor in your analog circuits.                                 •installs at speaker level ensures
Better transition with existing amp.

•11 band tunable with built in room
compensation deals with room peaks without over compensating 
Sealed system with proven speed.
•Works with all Vandersteen feed forward High Pass units unloading existing amp from heavy lifting 
allowing the whole system to play with better transparency and clarity.
JohnnyR

@willemj, Kenny is employing the GR Research/Rythmik OB/Dipole Sub, a very unique, untraditional bass reproducer, in a manner unlike a "normal" monopole sub. I suggested the Dual Core so that he could continue employing the subs as separate left and right stereo bass reproducers. While having multiple mono subs can provide benefits over a single pair of stereo subs, the OB/Dipole Sub was not designed nor intended to be used in that fashion. While the sub CAN be employed in the same fashion as a monopole, to do so is to squander it’s unique capabilities.

OK. I agree that a dipole sub is a great idea (looked hard for one but could not find one at the time). However, why does a dipole sub benefit from stereo where an ordinary one does not? Deep bass is not directional, and the advantage of equalzing in mono is that the two subs even each other out more effectively. This really is an open question out of curiosity.
I am just occasionally toying with the idea of getting these dipole subs, but I am not in the US, and they also seem rather large compared to the B&W PV1d that my wife finds only just tolerable (and perhaps rightly so), given that we already have the large Quad electrostats.