All three are completely different cars. The RS4 is a light sedan, the C63 is a heavy sedan, the E92 is a solid coupe that out performs the other two.
Oh, and don't get a paddle shift. Real drivers rake the gears. DCT is for pretenders. Robert Kubica is forced to use it, but what would Fangio say? Push button transmission is for the 1968 Buick. And, as far as I know, Buick finished out of the points that year.