Suggestions for suspension upgrades to a C320

[tditmire]

I have recently replaced the original wheels and tires on my 2002 C320 with 17" AMG wheels and some lower profile tires (all suggested for the C320 by TireRack). Now, when the car hits a large bump or groove at high speed and the car rides down on its suspension there is a nasty rubbing/grinding in the wheel wells. This is particularly bad when there are four occupants in the car and the car rides lower. I guess that the suspension is a bit too soft. Does anyone have any ideas (aside from reinstalling the rather unattractive original wheels)? Can someone suggest any upgrades to the suspension/shocks which might fix this problem?