I used the Circuit City brand Tsunami (made by metra) since I work there and IT KILLED the vibration completely on my rear wing, I also did use Dynamat on the door panels.
It's something I reecomend and if you do decide to do it, have a blow dryer handy, because that stuff works better when it's really hot and it alllows you to push in the dynamat in little spots.
overall, it was a good $15 investment.
BUt don't go to Circuit City to buy, WE CHARGE WAY TO DAMN MUCH if you not an employee.