The Maserati Quattroporte lost to a FWD Lincoln MKS in a head to head hill climb... and a Jaguar XF... and a Mercedes E550 (not an AMG)... and a BMW 550i (not M5). The Granturismo isn't going to perform significantly better. Even with the upgraded motor, a GranTurismo would get smoked around a track by a 5.0 Mustang GT. A few months ago, I saw a black Quattroporte with red leather. Stunning looking car in person. One of the best looking cars I've ever seen, but the standard Maserati range is not designed to be a weekend track car.
As far as the best looking car recenty. I saw an Aston Martin convertible last week. Didn't get a close enough look to see what it was exactly, and I'm not a fan of the convertible, but still a gorgeous car.