Will the Monroe Sensatrac shocks give me the smoothest ride?

I have a 1999 Buick Century. There are currently no problems with the shocks. I don't think my shocks will go out anytime soon. I am just doing some research to figure out what will give me the smoothest ride. Is it also a good idea to replace the springs the same time you replace the shocks? Or can you just reuse the springs?