some how i knew that pic would float up in this thread...
do you need the backseat? because you could always replace it with a big box with 2 12's and use the rest as your storage...
OR (and i dont know if this would work out like im thinking) build a custom box that filled in the floorboards of the rear passengers and put a glass top or covered anyways so that people could still sit in the back and put there feet down but just not all the way down...
what about those boxes that sit on the rear fenders?? would that work for you.
here is what i found at quadratec.com... but i dont know how much space it takes up... it does say you still have access to the cubby hole and jack...
Quadratec Exclusive ACTORY SUB - Cust...JK - Quadratec