The OP lives in Los Angeles and is considering all seasons? We don't even have snow here during the winter and I doubt you'd be going snowboarding or camping with a Z.
I'd stick to summer tires. If you want the best bang for the buck and don't plan on tracking the car, take a look at the Hankook Ventus V12 Evo's.
Hankook Ventus V12 Evo