1. we dont have shocks. we have struts.
2. what struts do you have on now? if they are the factory, how many miles are on them?
3. if you do replace the struts, you should also replace the strut mounts, as they tend to wear out on these cars.
anyways, a lot of guys go with new struts when lowering, usually KYB AGX or something similar. i, on the other hand, just had my struts replaced last spring and will have the SSC springs here tomorrow. im not changing struts again so soon, just not going to happen. its really all on you. if you are up at 60K on the factory struts, i would change them. i had mine done around 55K or so. its all on whether you want to spend a little more now or a lot more later, really. if you install the new struts with the springs, it should save you money in labor. if you have to do it later, you will pay full price for the labor, as the parts will not be off the car already anyways.
another point: when using the factory struts with lowering springs, you can probably count on wearing them (struts) out much faster than with stock springs. there would be more than the normal amount of stress on them, thereby shortening their life.