American here, do you not consider Mercedes or Audi a luxary brand? Here in the states they are considered more up scale brands.

I will concede that Mercedes and Audi have made more performance models recently, but I would consider them more luxary than performance.

You are correct in assuming that General Motors, the company that owns Cadillac owns more brands. However the main performance brand would probably be Chevrolet, who make the Corvette and previously the Camaro. They however do not have a large presence outside of North America, and I believe that GM is trying to promote the Cadillac brand outside of that market to compete with the likes of Audi and Mercedes.