Help - W124 rough ride

Hi,

I bought a 1990 W124 230E two months ago. The ride quality has been quite disappointed. Whenever it rides on (washboard) concrete roads, the front end tends to rattle and shake like a truck. Rattles can be felt on the steering wheel and floor. Turning left or right makes no difference but does not worsen the rough ride. Rough ride is more noticeable when car is driven for some distance from cold(about 2-3 miles). Sometimes slight knocking caused by rough concrete roads can be felt through the steering wheel especially when going up (worse) or down (better) slopes.

So far, I have replaced the four tyres (Bridgestones 205/60/15), front (Bilstein) and rear (Mercedes Benz) shocks, steering center link, tie rods, and steering damper. As a whole, there is slight improvement but long drives (one hour) still mean trembling hands and feet at end of trip. My mechanic has inspected the front and rear ends and is of the view that there is no OBVIOUS sign of a worn component that needs replacement. Wheel alignment is ok.

Please give views on what I should do next. Would the following new parts make any difference?
- Front sway bar mounts
- ball joints
- lower arm bushings
- wheel bearings

I have some photos of the front end (ball joints, shocks, lower arms) I can post but don't know how to do it.