After Market Struts?
 

I have a 06 c-230 sport, i want to change my struts, front and back make it ride smoother (not like it doesn't already) maybe make it handle better too on turns, but i don't want to spend a fortune either. anyone know some good after market struts worth changing the stock ones for?
Let me know if it's a good or bad idea to change them and just keep it stock.
Does anyone know if mercedes will void warrenty over something like this?
thanks.