In August I had my subs put together.
I am in Canada, so the price is likely higher than it should have been, but otherwise I am impressed.
Four JBL P1022s in a sealed enclosure, right around .75-1^3' per sub, all in one long box.
I am powering them with a modified RF 1501BD.
The subs themselves are beefy or at least appear to be, each weighing about 32lbs.
Upon installing them in the car for the first time I was very disappointed; the 1501BD wasn't modified at this point, and the subs, did not get loud at all. However, with the amp cool, I could definitely hear potential.
I finally found instructions to mod the 1501BD to run 1ohm, and did so, the result was amazing.
Listening to a variety of music, they really bring out those hidden, deep basslines, for example, Trust by Megadeth. They sound awesome with any time of music, making the drums in Cryptopsy feel like a machine gun, the bassline in Kim by Eminem, close to unbearable due to pain.
Overall, I would say these subs are awesome; especially for the price in the U.S. I spent probably $300-$350 per sub in Canada, I know they go for far less on ebay, or cardomain which is an authorized dealer.
I have been VERY impressed with these, they definitely hit lower then the two 15's (RFP 3415) that I used previously
Sorry if the review isn't awesome, its my first one, be gentle :)