The BMW M3 has long reigned as the king of the sports sedan segment. However, two new challengers have arisen: the Cadillac ATS-V and the Mercedes-AMG C63 S. The Cadillac was honed on the Nürburgring, and with its twin-turbo V6, packs 40 more horsepower than the M3. The mighty AMG, on the other hand, is based on the brand new C-class platform and sports a 503 horsepower twin-turbo V8. Does either challenger have what it takes to steal the belt from the M3? Find out on this episode of Motor Trend’s Head 2 Head.