I also think that everyone will have their own opinion, but 'm with 2fast. I have a base model with no mods and I found the road noise to be way too much. I know it's a sports car, but I don't intend to race it. I've added 40 sqft of second skin's damplifier in the doors, floor and rear area and then put 9 sqft of luxury liner in the rear area. The shipping weight of the package from second skin was 27 lbs. In hindsight, I wish I would have used the damplifer pro material.
The car certainly isn't luxury car quiet, but it's pretty reasonable and you can even hold a conversation with a passenger at freeway speeds. I think if you're adding sound equipment with the additional weight over the base stuff, then you're kidding yourself on keeping the weight off by not using the sound deadening materials. I suggest you go ahead and use the dynamat, add the sound equipment and just make sure you don't add the 150 to 225 lbs passenger.
