Dynamat is good stuff... main problem is weight (and $$).

It's not the lightest material.... but if you end up trying to go that route... don't buy the dynamat for $9 a sq. ft. or whatever they charge.

They sell similar material at home depot or lowes that comes in rolls (I think it's some kind of roofing material, the exact name escapes me).

MUCH cheaper, you just cut it to fit.

-Eric