I'd predict >140dB SPL capability in a tC, while still being "crisp" at lower volumes.

 

I've had both Kicker L7 12 and 15 and the 15 was not as clean as the 12. Plus most 15's and 18's are not designed to be SQ subs no matter the enclosure.

 

i'd say do the 4 tens. i have 1 10" Alpine Type-R in a 2cuft ported box tuned to roughly 28-30 hzs. it seems to play just as low as the 2 12's in a sealed that i had in my last car. i have always liked 10" subs better for cars. 12 and 15's are good for home theater but 10's are fine for a car.

 

you should just do 2 l7 12's, they are equivilent to 15's, evn in a sealed box they will poundddddd

 

The problem you have there is you were using the Kickers... Kickers aren't meant to be good SQ woofers right out of the box... they take A LOT of effort to make them soud good... I'm not a big fan of Kickers at all... I think majority of the time, they sound like poo....

Elemental Designs 11Ov.2, 13Ov.2, 16Ov.2, and 19Ov.2 will all sound very crisp and clean given comparable enclosures... it's just the design of their subs that makes them very SQ oriented...

 

well as far as SQ, I checked the specs and the infinitys' in a sealed box need .75 cf of air space, my box is.89 so guess will stuff some poly fill in each compartment, I dont think .14 off is to much of a diff

 

polyfill will make the subs act like the box is bigger than the .89... I doubt you'll need any at all...

 

3x12 is usually a great fit... it will pound really hard given the right configuration and the amp.. odd numbers of subs usually rival even numbers.