I have owned subs including a claw Mag, OZ ME, Soundsplinter RL-P, various infinity kappas, ED subs, a diamond TDX and an IDmax. In my opinion, the two best were the TDX and the Idmax, and the Idmax takes the cake. It is louder in a sealed box then many of these other subs in a ported box. It is efficient, it sounds beautiful.
My only complaints are:
1. It is expensive, and even though I got a really good deal on it used, it would be really expensive to fix.
2. It isn't as durable as other subs in this category.
3. Compared to other SQL subs, it needs a huge box. 2.5 cubes ported, and 1.5 sealed for optimum. That is a little big for my tastes, but I have been so happy with the way it has sounded in a sealed box that it has actually worked out OK.
Good luck!