Check the front shocks to be sure the long rubber bumpers are on the shafts, and in good condition. They should be 105mm long, and not all ground up on the ends.
Check the lower control arm bushings, the upper ones seem to last forever.
Check the guide rod bushings, these usually make a rattle/bump over small bumps or if really bad, when tapping the brakes. They really make the front feel sloppy.
(my money's on these as the culprit, ever changed them?).
Check to be sure the motor mounts have not sagged, and are allowing the exhaust pipe to hit the cross-bar near the steering idler arm; this makes a bad thump, but usually noticed first when accelerating and turning left.
Of course check the idler arm bushings for movement.
Check the steering damper.
I run the non-sport Bilsteins on my 300SE, and have changed just about every front suspension component over the last 17 years. Front is tight and solid, and takes tracks like they aren't there. As I said, only thing I ever found that really created a noticeable ride issue was the thumping guide rod bushing; couldn't feel any looseness when messing around with them on the car, but when I got them out, they definitely were loose; big diff.

DG