If you like your music rather than speed then yes, sound deadening would be a good move but it is pricey and extremely time consuming.
Dont buy into the Dynamat crap, they charge over the top for half the product. Look for silent coat as you can get it in sheets of 2mm to 8mm thick.
You'll need the metal sheets first, you'll only need to do about 50-75% coverage, with this stuff.
http://www.caraudiodirect.co.uk/silent-coat-mat-sample.html
Then ontop of that add this to stuff, it can also go under the rear bench.
http://www.caraudiodirect.co.uk/phonocar-soundproofing-panel.html
Also apply it and then use one of these.
http://www.caraudiodirect.co.uk/second-skin-roller.html
Its to make sure you have full contact with the surface.
Also with you upgrading to 6.5's, Make sure you use some of this behind your speakers to stop any moisture getting to the connections.
http://www.caraudiodirect.co.uk/phonocar-4-927-rain-stop.html
Set up the door for the speaker, put the sheet over the hole and put the speaker on top, as and when the speaker is screw'd down just cut the excess off and its done.
Once you have stripped the door down be sure to give it a damm good clean as it will be greasey as hell behind the panel.
If you do have some major power I will advise for you to have the side strips on the car to be taken off and padded out underneath also the heat sheild above the exhaust needs to be padded out, as they rattle like a b**ch on speed.