If you are tuning a box at 65 hz, you seem to be going for SPL.. If this is the case, perhaps you should consider using a bandpass box to target your specific frequency? Trickier to build, but you'll get a little more efficiency at the target freq if you do it right.

The best bet is to contact pioneer and ask one of their techs.. Tell them your are planning to do something *LOUD* and you want THAT target frequency peak, yadda yadda... Also, You'll need a few ports, so find out how many of what size and how long they will be, and box volume..

Thats the way to start.

ShadowStar