Fi-brations 10+ year member
CarAudio.com Elite
Installation is more important than equipment when it comes to spl. There are several members on this forum who can design a box for u. You need to decide whether you want a "burp" box for strictly spl and not music, a musical one, or something in between. A lot of factors go into gaining decibels, and it is almost all installation. Testing and tweaking over and over again. You should have a solid electrical within the constraints of the competition though like your working on now. Poor electrical strength will be a huge drag on trying to optimize the output of your amplifiers.