All you need is to use a product like Dynamat Extreme, line the inside of the outer door skin with it, and then line the door metal (in place of the plastic moisture barrier) with a solid sheet, or at least sheets so all the holes are covered except where the speaker goes. Place strip caulking on the backside of the woofer, and on the front side of the basket (outside of the surround) so it will seal to the door panel. This should help your midbass dramatically. Stuffing the doors w/ foam is not very effective IMO, and expandable foam has a way of messing up body panels when it expands.