Beginning in model year 2000, Mercedes drastically upgraded their sound insulation package provided on the ML's. This not only included additional sound insulation in the cabin floor, sides and roof but also double door gaskets. When I purchased my 2000 ML320, I test drove both a left over 1999 model that had significant discounts and a 2000 model. There was no comparison and the choice to purchase a 2000 model was very easy.

I still have the original Dunlops on the vehicle but had heard the Michelin Cross Terrains were quieter, however, at about twice the price of the Dunlops. The Michelins have a higher tread wear rating than the Dunlops so should last longer, but I have read reports from people who have switched to Michelin's from Dunlops and they did not wear as well.

You may want to look to see if your Michelin's have even tread wear. Any uneven tread wear or cupping will drastically increase tire noise. Since you have 70,000 miles on the vehicle I would guess that you have between 20,000 and 30,000 miles on these tires and tread wear may be a consideration.