Thinking of getting rid of my sub.
 

I've just acquired a Z28 convertible which is neat. First time I test drove it the seller cranked up the volume and as his head unit had the bass boost maxed out the sub woofer just made this dull booming noise which didn't really sound like music. This might be cool for people who are into loud noises, but I think music should sound like music. The previous owner was pretty happy with this set up.

In the trunk is some heavy duty gear. There's a McIntosh amplifier and a JBL bass tube which between them takes most of the space in the trunk - hey but that's why manufacturers put a trunk in the car, so I would have a space for the AV system right? Problem I can see is the trunk is sealed fairly tight. The only way for sound to get out is for the subs to vibrate the panels and the rear seats and for these to make some noise.

Unless I can find a way to port the bass into the passenger compartment, I think I should get rid of the bass tube and maybe put 6x9's in the back - there's already 6x9's in the front.

Talk to some car stereo shops to get some ideas before you decide your final approach -- might be best to take your car to the shops. Let us know what you decide and POST PICS! ;-)

I have a convertable with 2 12's in the trunk. You can make bass that sounds good and doesn't rattle your car to death. With the top up you can remove the panel that seperates the cab from the trunk and that will help a lot. With the top down there's not much you can do, the bass is just going to be less with that thing in the way. With my system I really don't have much rattle, the spoiler rattles and I haven't been able to find anything to make that stop. The lincense plate will rattle also, some two sided tape on the back of it will stop that.