I recently put HDs at all 4 corners on my '92 300D. I also upgraded to 16" X 7.5" wheels with 215/55-16 tires (yes I know they're too tall-will be replaced w/ 225/50s). Before the HDs the car was way too uncontrolled, especially at higher speeds (65mph+) and felt too softly sprung. With OE 15" wheels and the HDs, the damping was clearly more aggressive, and rebound quicker. Diminished ride quality a small bit, but assuredly worth the payoff in control. Still too softly sprung, though.
Now, when I installed the 16s EVERYTHING improved, and I don't quite understand why. Ride quality's slightly improved (near OE now), damping is perfect, body roll is diminished and the springs feel about right (for a luxury-oriented car).
Just my $.02...hope it helps.
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car