Unfortunately, there are many choices for sound deadener. ONe of the newest ones, which is pretty popular right now is SecondSkin Audio (
http://www.secondskinaudio.com/cgi-bin/index.cgi). SecondSkin has different types of deadener, both the stick and spray type, in different thickness and grades. I am thinking about doing my current project truck with the Sprectum and Damplifier. If I get to that point, I will let you guys know how it works.