Don't do it. On a car with chronically weak strut mounts, the added stiffness of the Bilsteins transfers even great loads to the strut mounts. After putting Bilstein TC's and new strut mounts on my S80, it tore through the strut mounts in less than two months. Volvo's parts warranty picked up the replacements but not the alignment or centering the steering wheel which was another $185.00. The replacement strut mounts lasted just over ten months(just out of parts warranty), until I went over a bump with four people in the car, and both strut mounts broke simultaneously. At 145,000 miles, my car is on it's third set of shocks, (the OEM shocks seem to fail catastrophically after about 60K miles), and the fifth set of strut mounts.
I put the Bilsteins in because the OEM shocks were trash, but it just served to exacerbate the trash strut mount problem. It would seem that every solitary part of this car is trash.
When you consider a car as nothing more than the sum total of its components, its clear why Volvo can't give this car away.