The 2006 models bring a slight change in 6 Series nomenclature and more of what we like best in this car: power. Thanks to a new engine, the 645Ci Coupe and 645Ci Convertible have become the 650i, respectively. The new 4.8-liter V8 is slightly larger than its predecessor with 10 percent more horsepower and torque. (Apparently 648i didn't have quite the ring as 650i.)

Other changes for 2006 include new wheel designs, new exterior colors and some interesting, if minor, tweaks inside. Active Steering, a high-tech BMW system appreciated by some driving enthusiasts and hated by others, is now a stand-alone option and no longer required as part of the popular Sport Package.

The coupe and convertible are essentially hard- and soft-top versions of the same car. Bristling with the latest technology, they are not simply two-door versions of BMW 5 Series sedans. The 6 Series is a modern interpretation of the classic GT, or Gran Turismo.

While both the coupe and convertible have a back seat that can fit small people in a pinch, they are really intended to move two people and their belongings in high comfort and style, safely, at truly impressive velocity. The 6 Series offers more luxurious accommodations than BMW's Z4 sports car, yet with higher performance, more agility and sportier styling than the 5 Series sports sedans. BMW's corporate design themes, panned by many in recent years, seem to fit better on the long, low 6 Series.

All 6 Series buyers now get complimentary high-performance driving instruction at the BMW Performance Center in South Carolina. It's a nice ownership perk, because the 650i Coupe and 650i Convertible each qualify as an ultimate driving machine, and the chance to try them on a track will be well-appreciated. Yet either can be driven all day in the most mundane driving situations in perfect comfort. These cars might just represent a well-respected automotive marque at its very best circa 2006.