Two subwoofers in smallish HT room?

I design rooms with multiple subs often. I agree with Rives about using two subs and room modes. They know what they're doing. This is one of the hardest things to get right in any home theater. I really dislike locating a sub that's near my seating area even if the bass is great. I strongly believe that the room's low frequency room behavior needs to be looked at first (test the room, our ears can easily deceive us) and a few questions answered:

1) Were you happy with the bass except for the low output? If you were happy except for the output I'd get another bigger sub and try it out using the processors crossover. The then play around with placement if needed.
2) The Vandersteen needs it's own crossover and your main L/R amplifier as per it's instructions unless you carefully changed it's hook up. It makes it hard to use it as an LFE.
3) If you still want to use two Vandersteens (or any two subs), although very good subs, their hook-up make them problematic to use. I'd probably try two identical of a different brand. I'd need to carefully set them up by taking measurements which can be done with a simple Radio shack meter, a free audio generators through your computer as a source or a very good CD that has very closely spaced frequency bands and a piece of graph paper. It's time consuming but very enlightening about bass performance.

That's good news. I saw Richard Vandersteen at CES and I failed to look up the newer sub. I mostly looked at his speakers.

What you could do in a pinch is stack Vandersteen subs. You get significantly more output with another sub (not double but say 3-5dB. 3dB officially but it depends on how they react in the room). That's often enough to satisfy people. Kevin Voecks used to do that at shows to make sure he had enough output to satisfy a crowd.

I think you still need to look at the room behavior to find out if your dealing with a big frequency hole next to a big peak to make sure that your not fighting another battle. Adding another sub in the smae location won't help you then. If you have some time and want to learn the subject, especially about multiple subs, try Dr. Floyd Toole's white papers on the subject, http://www.harman.com/wp/index.jsp?articleId=1003.

I use a small and free tone generator named NCHTONE, http://www.world-voices.com/software/nchtone.html, from of the headphone out of my laptop to my system when I don't wnat to setup my complete testing system. With that and a Radio Shack meter you can make a graph of your system's behavior and pretty much KNOW and not believe you know what the problem is.