s10L7 best at what HZ?

Buy a test cd with different tracks at various frequencies 20-200 hz.  One of the autosound cd's has these tracks, I believe.  If you are talking about that bandpass box though, be careful with test tones or you can damage your subs.  And if it is the bandpass, the behavior the other members were talking about is typical of a bandpass box.  If a frequency falls outside of its tuned range it will be much quieter that the other bass "notes".  Bandpass boxes are not known for quality sound.

Nope, I still have it in the box the Dealer made for me. its that 1.5cm and 2.5cm something like that. Its made to optimize the speakers according to kicker, Its in a sealed box but i would love to get it into a bandpass box cause i heard those make all subs sound a whooooole lot  louder dunno if its true or now. as to what bryceyaworsky said with the thread above 20-60hz is where it peaks out. some songs go crazy and now i know why. What do you guys think about my bandpass idea. Will it make a huge difference like it did to the cheap no name brand subs i bought or will it just get a little louder? Also anyone know any good cheap 40WRMS X 4 amp?

bandpass will make it much worse if what you're worried about is a flat response.  What you can do is either add some 6.5"/8"mid-bass or 8"/10" subs and run them at a higher frequency to fill the gap.

Of course you would gain some volume using a vented or trying to use a bandpass box, but then you would be severely limited regarding what you play since the frequency roll-off would be much worse.