After I installed an aftermarket amp and speakers in my NC, any time I would turn up the volume even a reasonable amount, the doors would rattle like crazy and sound cheap. I ordered a bulk pack of Damplifier Pro to add some sound deadening to the car to cut down the rattles. I started by adding about 1 and a quarter sheets in each door and I was so impressed with the result that I was happy at that. The doors now have a much more solid thud when they open and close rather than the tin-can sound from the factory, they don't vibrate with the stereo turned as loud as I can comfortably listen to it, and the doors no longer vibrate under acceleration (with my RSII exhaust). For the minimal cost, effort, and weight penalty I think it is well worth adding this small amount of deadening to the doors. The installation is very easy, just remove the door panels, remove the plastic pieces in the doors (just a few 10mm screws) then peel and stick to the inside door skin.
I'm selling packs of 3 sheets (5 square feet total) of Damplifier Pro Sound Deadener and Vibration Damper so that other members can deaden their doors too. 3 sheets is more than enough to do both doors and you'll probably have a little left over to add elsewhere if you would like.
For those concerned with adding weight to their car, keep in mind that if you use all three sheets you will be adding three pounds to the car.
I'm passing on the savings of my bulk order to you. Price for 3 sheets from Second Skin is $55 shipped, I'm asking $45 SHIPPED for each pack of 3 sheets. If you would like to purchase more than 3 sheets please contact me and we can work something out!