The 2011 Cadillac CTS-V Coupe actually overlaps with the BMW 650i and the M6. Handling and acceleration are closer to those of a 650i, while top speed is on par with an M6. The CTS-V is not as effective in delivering full output like the M6 due to a more conventional gearbox, a higher drag area, and even worse, a higher-end torque curve.
The automatic is limited to 175 mph, but I think it can do 200 (some 9 mph faster than the manual due to the closer ratios between gears 5 and 6); 195 headwind and 205 tailwind. The V2 CTS-V (particularly the sedan variant, which was even rumored to reach 198 mph with a 6-speed manual) apparently has better aerodynamics than both of the forthcoming generations that suceeded it, including the V3 CTS-V and the CT5-V Blackwing.