Changing springs is mostly personal preference. I personally prefer to neutralize my handling with sway bars if possible. Changing spring rates can certainly be a great way to neutralize handling but at the expense of sometimes teeth jarring ride.

I believe that the combination of heavy duty Bilsteins and a 500E, or even stiffer rear bar is the right combination on the 124 car. I have comforts on mine and like it even better. Shocks play into the handling equation very little as far as oversteer/understeer goes. They do play into handling from the standpoint of keeping the tires in contact with the road surface. Thus, shock and spring choice will be greatly dictated by your road conditions. If you sometimes drive on rough road surfaces WHILE CORNERING, then shocks will play into the equation.

Good luck,