If you are worried about insurance rates I doubt you will save anything moving from a Camaro SS to a BMW. Parts are more expensive for BMW, and the value is higher in general.
By the way, I drove all the newer muscle cars (Mustang GT 5.0, Challenger R/T, Camaro SS), and other than the fact I liked the Camaro the LEAST, the feeling of a BMW is just completely different. Even if the numbers on paper of the muscle cars are better, the overall completeness and refinement of a BMW is something that cannot be beaten.
Keep in mind that in general, a sedan will be cheaper to insure than a coupe.