short answer: No.
i know of 2 companies that made superchargers for the 3.6L CTS, one was Lund, the other company's name i cant recall. Either way, nothing ever made production. If there was enough demand, there are companies that would make one for it.
No turbos that i know of.
but if you keeping your CTS comes down to "if i can turbo/sc it, then perhaps i'll keep it, if not, i dont want it" .. then you'd probably be happier selling the CTS, and using that $ you'd be investing on a maggie or turbo towards a

....you can get an 04 cts-v for 23k, easily.
good luck.