coustic xm3 corssover

has anyone ever used this crossover, not the xm3e but the xm3... i;m gonna use it with a RF power amp with a  24db butterworth crossover. i;m using a crossover becuase i only have 2 pre outs on my head unit. IS there big difference between the coutic xm3e an the xm3, becuase the xm3e uses a 18db for hipass and the xm3 only has 12db. Will this make a signicant difference.... and another thing will the crossover on the amp be better to use by itslef if i had 3 pre outs on my head unit..

thanks..

a pair of 6 1/2 Infinity Kappa componect 3 ways up front in my doors

a pair of 6x9 Infinity Kappa 692.5i 2 ways in my rear

and a  4 channel fosgate punch  amp to push them  400watts rms 4x100 4 ohms

then two Kicker L5 12" subs powered by hiphonics 2x500rms amp

Head unit with 2 pre outs

i heard from guys that the external crossovers like the coustic xm3e makes their system sound a bit better.

but i just bught the coutic xm3, any reviews on it versus the xm3e

Ok... and you're just wanting to cross over between the subwoofer and the mains, correct?

Anyway, check out this:  http://www.bcae1.com/elecxovr.htm

It will tell you a little about crossover slope.  I personally like a steeper crossover slope than 12db between the mids and subs in car. 

I think I would just use the crossover in my head unit, personally.  Any external device like that is just another chance for more noise to enter the system.