I actually purchased a big bulk pack of Dynamat from amazon (btw - they have the cheapest price online and shipping is free to boot) and I've been slowly working on doing my doors. It makes a slight difference, but I'm expecting to see a big difference when I do the roof and floor. I've got my sport lights on top and they tend to make things a bit noisy.
So far, I've done 3 doors. The bulk pack has 9 sheets, and one sheet does one door. I'm ~hoping~ I might be able to cover the floor with the remaining 5 sheets, but if not, I'll do the roof, buy another back and do the floor and may a few other places. Main reason I want to do the floor is cuz I want to run some wiring under the carpet for a new amp I've been sitting on for my 4 door speakers since last winter.