Crap I wish I would have seen this earlier.
You need a blocker material. Not an absorber. Abosorbers are good for high frequencies, but what you are trying to do is limit the amount of road noise coming into the vehicle which is all lower frequencies. That carpet underlay is a high frequency absorber, not a low frequency blocker.
Study the differences between NRC and STC-they are different.
Mass Loaded Vinyl (MLV) is a good blocker and probably the best material you will find for the money. Deadener is good for reducing vibrations of flat unconvoluted panels-but it also lowers the resonant frequency of the panel. It is not a good blocker/barrier. The foil helps block noise, but it's much more costly to line your entire vehicle with multiple layers of it.
http://www.noisedead.com/ John is a good guy and will help you out.
Second skin also has their luxury liner pro
You might be able to find commerical places that sell it as well.