Cadillac’s halo sedan combines luxury appointments, prodigious power, knife-edge design and finally, lithe and lightweight construction. To this point, Cadillac claims that the CT6 weighs less than the Mercedes-Benz E-Class and BMW 5-series sedans, while weighing about the same as the smaller Cadillac CTS (the CT6 is about 8 inches longer between the front and rear wheels). Assisting in the pound paring is a 100-percent aluminum body and front suspension. The four available power teams have been joined by a 550-horsepower twin-turbocharged V-8 that’s exclusive to the new all-wheel-drive CT6 V-Sport model. The rest of the powertrain lineup includes turbocharged four-cylinder and V-6 engines plus a non-turbo V-6. The plug-in hybrid CT6 uses the turbo I-4 plus two electric motors for a maximum 31-mile range at speeds up to 75 mph in electric mode. The plug-in’s output is sent to the rear wheels through a continuously variable transmission, while the gasoline engines use an eight-speed automatic (10 speeds for the V-Sport). Among the CXT6’s options are all-wheel-steering, Quadzone climate control, articulating heated-and-cooled rear seat with massage and a Bose Panaray sound system with a total of 34 speakers.