The Mercedes CLS is roughly the same size as the E-Class sedan, with which it shares a number of major components. Yet the CLS-Class features fewer variants than the E-Class and it occupies a higher range on the price scale, with more standard luxury equipment. What distinguishes the CLS most readily from other Mercedes sedans is its four-seat cabin and gorgeous exterior styling. It comes in two varieties: powerful and crazy powerful.

For 2007, the CLS line features new V8 engines. The baseline is now the CLS550, powered by a 5.5-liter V8 introduced in the full-size S550. This engine is considerably more powerful than the one it replaces (in last year's CLS500), yet without a decrease in fuel-economy ratings.

The super-fast 2007 CLS63 AMG gets a new, hand-built 6.2-liter V8. With 507 horsepower and 469 pound-feet of torque, the CLS63 is one of the most powerful four-door cars available. For 2007, the CLS63 also gets a new seven-speed automatic transmission, replacing the five-speed previously used in AMG cars.

While both CLS models offer performance, it's styling that distinguishes the CLS. Technically, the CLS is a sedan because it has four doors. Mercedes calls it a four-door coupe, and that's a good description. The swoop-roof, pillar-less CLS has the graceful, sensuous, feel of a coupe with the rear-seat access of a sedan. Whatever it's called, it may be the most visually appealing four-door on the market. Those great looks come with a slight penalty in terms of interior space, of course. The CLS only has four seats with four seat belts, while the E-Class cars have five.

In terms of technology, however, the CLS gives up nothing. Its air-spring suspension automatically gets firmer or softer depending on road conditions. A vast array of Mercedes safety features come standard, including rear-passenger side-impact airbags and one of the most advanced skid-management systems in production. More than 70 percent of the steel in the body and frame is galvanized, high-strength alloy, and even the paint is advanced. The clearcoat layer is impregnated with tiny ceramic particles, increasing resistance to scratches by 300 percent compared to conventional finishes, according to Mercedes.

The CLS is unique among luxury sedans. It's a must-see for drivers willing to exchange a rear center seat for a load of curb appeal.