i think for spl the most important thing is the box. i have a box sitting in my room that used to have 2 10' audio pipe subs with a ma audio amp and i hit 139.00 my amp was the low level amp and we all know what audio pipe's quality is but the box was solid, and it was huge. TBSpyder worked at sound advice he might know the box i am talking about it was ment for a suv but i put it in my integra.
but none the less when talking about spl the most important thing in my opinion its how good the box is expecially when the box is vented.