Well I'm going to try and not sound like and Elemental Designs fanboy here...(I am one, just don't want to sound like one). but...
http://www.edesignaudio.com/ed...e.php
eDead products are much cheaper than dynomat. I've used the fatmatt previously mentioned and it sucks compared to edead. also Edead is now butyl based so you wont get that smell somebody else was talking about.
so as maxnix was saying, to battle low freq road noise you need to add mass. all the deadening has to do is make the panel your applying it to heavier. to battle higher freq road noise they have a product called V4, Teklite. not really sure how that works though.
another thing I have to add, my Y33 is the quietest car I've ever rode in by far. the next closest thing would be my inlaws 2003 camry and I think thats only because it has a quieter engine (half the cyclinders hehe).