BMW calls its midsize X6 a Sports Activity Coupe (even though it has four doors), presumably because of the X6's sporty and graceful profile. There's no doubt that the X6 is a premium head turner. What you get for a less premium, however, is a surprising amount of performance. The results from our testing of the 300-horsepower xDrive35i model are closer to those of a sport sedan than an SUV. And what is even more shocking is that the X6 weighs almost 5,000 pounds. Its ability to quickly accelerate, corner and slow down defies logic, and to BMW's credit, the X6 also provides a comfortable and quiet front-seat ride. For those who hunger for even more performance than that from the standard twin-turbo inline-6, there is the xDrive50i that boasts an over-the-top twin-turbo V8 producing 400 hp.