I just replaced the box in my car with the one that PV Audio designed for me. All I can say is that both my jaw and the installers dropped wide open when we turned the system on right after we got everything hooked up. My installer told me that the box had perfect frequency response from bottom to top. We were debating before the install how we were going to squeeze 6 x 9's in the back to accomodate the mid range however the new box solved this problem for us.
I know my system isn't anything special but I tell you the two 10's hit nice and hard and have a great response scale. I can really feel the bass now! I can't complain one bit.
Just wanted to give props to PV for a great design and let the rest of you know you he's got my vote and recommendation.