I just finished the fronts on my 2005 CLK55. The car has 52000 miles, the pads were thin and the soft Mercedes rotors were worn. I installed RacingBrake 2-piece rotors (model 2270) and Porterfield R4-S pads. The installation was easy, everything fit perfectly and the pads bedded nicely.

 

I have Porterfields on my CLK550 and I like them. Almost no dust, and good stopping, but I still think, at least on mine, OEM is the best (if you can stand the dust).