Well I've decided to go ahead and upgrade the full system.
What I've got so far
•Polk Db6501 6.5" Components
•12" Infinity Kappa Perfect Sub powered by an 800w Pioneer Mono Amp

The plan
•replace the rear 6x9's with a pair of Elemental Designs 6.5" subs
•power the front and rears with an Alpine PDX-4.100

I've been reading the threads by others who have done this, here and here. DanSeals has an excellent gallery of his install, and that I'll be trying to emulate.

Now for the main question:
What I'm not so sure about is how to go about sealing up the rear cavities. The descriptions I've come across have been fairly vague, mostly use sound deadener.

I've ordered a pair of baffles for the front speakers. After much research I'm leaning towards the CLD panels by SoundDeadenerShowdown for the door, the rear panel and the hatch. I'm only looking to reduce vibrations, I'm not looking for a completely silent ride.

I'm also leaning towards edead for the inside panels. Opinions seem to be varied, with most of the negatives coming from a couple of years ago. Some people seem to have had decent results with Peel and Seal. I live in Florida, so I don't know if I want to chance having it melt on me.

If someone could point me in the right direction for sealing up the rears, or if you have any thoughts or ideas about this idea I'd love to hear them.

 

I used builders foam in the rear 6x9 locals to seal them up, along with some DPro. Worked great for my subs, and wasn't all that difficult, just don't go crazy with the foam.

 

Still need any help?