they are fantastic! SQ is great, low end is great, efficiency is great, they get loud also in the right enclosure. They are one of the best all around subs out there.
Yes. This sub is VERY efficient. I had one in my s2000 in a 1.75 cufu vented box and it bumped! sounded great even though it was in a convertible. I used it with a Hifonics BX-1000D.
I took the sub out because I sold the car. I'm currently getting a 2.8 cuft vented box professionally made (but designed by Image Dynamics) right now. It's going hit HARD! (and still sound good). By the way I listen to hiphop and trance, and they both sound good on the sub.