Seeking a bit more bass, I experimented last weekend with re-integrating my Velodyne DD-15 sub in with my system. To be brief - Holy COW!! I have the sub coming in at 33hz with a slope of 18. The change in sound is nothing short of amazing. This sub has finally been replaced by Velodyne in their line with the DD-15+ which is more user friendly, a bit bigger and a 39# magnet. While tempting, it is not a critical upgrade at this point.
It feels as though the 7's bass drivers have even more slam, both due to the sub plus the fact they are no longer having to drive anything below 33hz. Moral of the story - if you have VSA speakers (other than 9's) you will probably benefit more than you could ever imagine by integrating a good quality, fast sub into your system. I had no idea how much additional low bass information I was missing - it has now been found! This was a real "AH-HAA" moment for me, so I thought I would pass it along to other VSA owners As always, YMMV...

Harve