I would like a pair of subs in my '96 9c1 but don't want to take up much space. I already have a set of CDT 6x9's in the rear deck. Hack sells that backboard that sits behind the spare tire with 10' cut outs. This piece is a pressure fit. I have also seen the boxes that run along side the spare tire and output behind the rear seats. Which of these sound better and is sturdy?