Thanks guys, seems like everyone's had the same concerns at one point or the other...I do share TWO walls and a floor with neighbours so I'm flanked on all sides.

Even with the m60s I can feel the floor vibrate so I shudder to think what an HSU or rava would do....but I'm at the point where I'm craving the meat in my music!

Has anyone had the opportunity to compare side by side a sidefiring and downfiring sub tho' and how it affects the listening/FEELING experience?