I had 2 of these running off of a Lanzar VIBE251 in a prefab sealed box. For around 70 dollars for each of the subs, they were a good deal.
They hit pretty hard and definatly shook up my whole car, but the SQ wasnt taht great. Also, you cant really hear these subs outside the car much if you are planning on trying to show them off. Great for a first system though.