not sure about the vibration, i lowered the car 30mm using eibach springs, and then had the geometry set by dealers . i too had a problem with the car wandering it was also difficult to keep in a straight line and would follow the road towards any slant, camber or poor road surface, ruts etc. the steering would turn excessively, especially on braking.
was also told lower ball joint was worn, but got it double checked independently and it was fine.
have you got any irregular tyre wear? mine was showing signs of wear on the front outers, so i took it to an independant garage and had the geometry set, all i can say what a transformation on handling it now drives perfect with non of the problems i listed above mate.
have you had the geometry checked?, even if you have i would get it checked again may be elsewere!
i now love driving the car again, it feels like a new car even though it is six years old!