I used Raamat. People here and at Montecarloss.com have recommended it before. It can be bought through here http://www.cureline.net/lex/raamsale.htm
much cheaper than dynamat or others and seems to work very well. After having the Nakamichi stuff mounted on the doors, make sure the crossovers don't rattle internally as my Naks do. I had an irritating rattle in the right door at certain frequencies and after taking the panel off numerous times, it ended up being the plastic cover on the crossover box and the circuit board on the inside of it. Very annoying. Of course, if I would've mounted the crossovers somewhere else, I would not have had this problem. The new Morel crossovers are going in the same place, but don't appear to rattle at all as they are solidly encased in plastic.
The door metal, once you remove the plastic panel, just has a vinyl-like material covering only parts of the metal door. If you Raamat it, you'll block a lot more road noise. I didn't even bother putting the OEM piece back. I just saved it in case..I think the most road noise comes from the firewall (which I didn't spend time covering), but covering the doors did help a little. There are a few gaping holes in the door panel (weight saving? access to window mechanisms..).
As far as the Nak amps? I am happy with anything I have ever seen or owned from Nakamichi (my sub is very well-built looking). I think you'd have no issues. I am running two MTX amps which I guess would be in their mid-level line?? They perform fine. I don't have any first-hand experience with the car amps, though. There are a lot of folks here who have some good advice on amps, though. I think as long as you match an amp to your speakers properly (real RMS numbers) you're going to be happy.