Sound deadening, I'm doing 40 sq ft this week. Did it my rx7 (king of drone) an cut the dound in half. Keep in mind asphalt based deadening is crap, you need thick butyl to make a difference. I use qmat, it was about 140 shipped for 40sqft.
Keep in mind that once you start down the road of sound deadening, you will want more and more. I ran a car audio install bay for both Best Buy and Circuit City for a long time.
My most crazy car audio build I had a 97 Lexus SC400 and I to every square inch of the interior out besides the actual dash and went to town with sound deadening. It included:
90 Square feet of Dynamat Extreme
5 Gallons of Second Skin audio Spectrum sprayed in to the car
10 LB box of polly fil stuffing stuffed into all of the open areas of the frame and ect. inside the car.
Big roll of carpet padding glued to the back of all the panels ect. and stuffed into lose areas
A case of the Duplicolor under coating sprayed into the trunk and around the gas tank (tank was behind the back seat).
The result was that car was so quite you could hardly tell it was running. Once you get to a certain level of quite it sucks because all kinds of things you didn't think were that noisy before become noisy. All sorts of switches, the fan motor, even the weather stripping around the sunroof was old and leaked a little wind noise and it drove me crazy buy Lexus would only sell the weather stripping together in kit with he sun roof glass for $1400.
And don't EVER, EVER pay retail on sound deadening products like Dynamat, it's the most marked up stuff ever. Stuff like the 30 Sq ft kits of Dynamat sold for $100 in Store, but our price was only $33.