If you are concerned about depreciation, please check out the prices of a couple year old AMG's. They drop like a stone, very un Mercedes like.
I know the 02 S55 did not have the supercharger, but people who bought them are already down $25-$35,000.
I also have experienced the power of the CL55. While it is a fantastic car, there is no drama. The car simply will not let you anywhere near the edge before the electronics kick in.
Extra Supercharger enhancements are available from "THE VIPER SHOP" and Dan Cragin In LA. He also works on AMG's.
Enjoy your new supercar.