KYB Shocks are firm...will my car suffer?
 

I just had rear shocks put on my 1989 Volvo 240 DL Sedan. They feel kinda stiff. I called the manufacture and they say that for the part I have...the KYB GR2 343010... that it is 10-15% more firm than the original shocks. The city I live in has really bad streets with alot of pot holes. If these shocks are firmer, is my car going to take more impact from the road and make my interior parts(or any other parts for that matter) come loose after time?