You done bought a Mercedes. The tires are going to be expensive! We've got a Volvo 850 Turbo that calls for Z rated tires. They're pricey... I have no brand advice for you, but personally I prefer to stick with brands I recognize: Bridgestone, Michelin, Pirelli. Had good luck with Pirelli P Zero Mud and Snow last time around. This time I had to buy cheapo tires in Oregon since there was snow and my FIL swore that our Pirellis were bald.

I am the Doctor, and THIS... is my SPOON!