[Duc Hunter]

DO NOT COVER THE WHOLE AREA WITH AN MODERN SOUND DEADENER LIKE DYNOMAT!!!!

That is about the worst thing to do. Water WILL get under it as some point, and it will cause massive rust quickly, as the water will not be able to evaporate. My rear seat area suffered this, and I pulled it out. A foam sound deadener would be good, as the water won't get trapped under it and can dry more easily, and you can feel if there is water in there. IMHO too, the read deck lid and vertical surface can use the sound matt for sure, but the seta pan wont really buy you much.

as an aside something like Dynomat does not need full panel overage. Strips on each panel will do as much as full coverage. It basically kills the "tinny'ness" of the metal, reducing the "ping" vibration related noise of the panel. Think of a stone hitting your floor pan. No sound deadening and it goes "ping" and rings/resonates. With something like dynomat or the factory asphalt it is more of a deadened thud. To lower the Db of noise overall though, you need foam. As I understand it, and I am no expert, you need them of multiple density's.

Are you planning on running the engine bay sound mat, and the deckled interior sound mat? If not I would say don't worry about sound proofing the rest of the car, as it would be like pee'ing on a forest fire. If you are, then certainly explore sound deadening other areas as well. Just my 2 cents.