Dynamat is good stuff. I used a product called second skin audio. Very similar to dynamat but cheaper. http://www.secondskinaudio.com/. Try this link for some more info.
I researched the subject to death and also used secondskinaudio's damplifier pro. I don't regret it at all but I didn't find that that it was an amazing night and day difference. More of a small difference. My exhast had a terible drone so it was hard to tell. The one thing I wish I would have done is add some kind of heat insulation blanket. I still get the exhaust heat coming up thorugh the floor.
I tried to put it in the doors but it wouldn't stick.
