I run a set of the 15.4's. The hcca are designed for a smaller sealed enclosure, but I put mine in a ported one, hooked it up to a kole audio kx1-5500d (stock electrical except big-3 -bigtime underpowered...),and got 138db out of the termlab in carlisle this year. Since then, I've tweeked a few things and even though it is not really accurate, I've gotten 153 out of my epic 160 with this amp and subs and I know the subs are laughing at the amp... My personal opinion of these subs is that they can get low with (almost) the best of them, and that they are loud as hell. Even though you can db drag with them and do well, they are more of a musical sub if ya know what I mean. Shipping included, I paid $440 each for mine and I think they were worth every penny and then some. Here's link to two videos I took while I was breaking the subs in. This is before the epicenter and all the tweeking.