Don't waste your money on overpriced Dynamat...
www.secondskinaudio.com
Anthony (owner) is a great guy and is the most knowledgeable deadening person I have EVER met. I've bought from him ever since he founded his company, great products and great business.
Check out damplifier and liquid Spectrum.
Go to product specials, pick up b-stock for less (still same performance...just diffeent packaging etc...etc...)
I have over 120 sq. ft. of Damplifier and 1 gallon of spectrum in my truck. It did WONDERS for me, especially since my 18 was tearing shit up.
Secondskin is equal to or better in acoustical dampening properties than any other product on the market. It also has the absolute highest heat tolerance...so never have to worry about it peeling off in the heat.
So check him out, Anthony will treat you well.
-Noah