Subs for Audio Physic Virgos....

I am using a Velodyne HGS-18 to great effect. It is placed in a corner and set at the 40 hz crossover level. Volume is relatively low, but (using measurements and ears) adds just enough bass to make room response flat down to 15hz.

I run the sub off the high level speaker posts of my bel canto evo2 amps. Preamp is a BAT VK-50SE.

I used a single Luna with my Virgos...Rhagen is right, I'd love to have another one, unless you put it in the center between the speakers, the sound does seem asymetric - please ignore what they say about the directionality of bass information. Placement is VERY important. I'm using the Luna with Ref3a monitors right now. (I still have the Virgos). But, I'll have to say I've never heard a sub really integrate with the main speakers. I think the information from 30 - 40 Hz is what you are missing, and that is hard to 'fill in' with a separate box. I'm glad I own the sub, and I use it, but it doesn't solve the problem of not having a pair of good speakers with output down to below 30 hz. Of course, if your room is small, as is mine, full range speakers can sound boomy. A sub allows you to control the level.

The audiophysic subs will give you the best shot at integration. great match...

I used them with a pair of corner placed AP Lunas. It did
wonders with the bottom end of my system. The trick is to
use a pair. It gives better dynamics and you will not
identify their position as easily as when used alone.