Many of the "early adopters" messed with our original cars quite a bit.
I installed a leather interior, and while doing so, upgraded the speakers and added dynamat sound deadening to the doors.
Here is a 10 page thread, with pictures and diagrams of how most of us did it.
(possibly why no one rushed to answer you
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There are a couple of tricks in there, which are nice to know going in.
Worked well, and still sounds great.
(also made closing the doors sound less like a Coke can)
Added about 70 lb's of weight, but I considered it a small price to pay