After struggling for years to keep up with the imports, Cadillac has finally hit its stride and the STS proves it. The STS is the 2006 successor to the Seville, which was originally introduced way back in 1956 as a hardtop coupe designed to be the top performance option in the Cadillac lineup.

A 305-horsepower V8 engine and exclusive high-end interior trim ensured that the Seville was not only one of the fastest vehicles on the road, but one of the most luxurious as well. Cadillac shook things up several decades later when the all-new Seville was unveiled as a high-performance sport sedan capable of keeping up with the best Europe could offer.

Cutting-edge styling, tighter build quality and the addition of a new sport model called the STS made Cadillac the talk of the town. The introduction of the ultrahigh-tech and powerful Northstar V8 a year later further cemented the STS as one of the top performance luxury cars in the world. Another redesign for 1998 saw the Seville pick up a sophisticated array of in-car electronics. By the beginning of the current millennium, though, it had lost some of its appeal, as European and Japanese competitors surpassed it in both luxury and performance.

Cadillac has dropped the Seville name for 2006, but the revolutionary new STS definitely shares some DNA with its forebears. This car represents a quantum leap forward in technology, build quality and overall refinement. GM's globally developed Sigma platform cut its teeth as a successful backbone in the CTS, CTS-V and SRX, and was tapped once again to lend some performance cred to the big boy of the Cadillac line. Hard-edged styling introduced a few years ago on the Escalade has been trickling down to the rest of the Cadillac line, and we think it has been applied most successfully here.

Clean, elegant lines on the outside work with loads of leather and wood trim in the cabin to form a lasting impression of quality and luxury. Extra attention was given to reducing road noise, and details like a quiet steel dash, triple door seals and even "airfoil" windshield wipers designed in a wind tunnel all contribute to making this the quietest GM vehicle ever built. Engine options on the Cadillac STS include a refined new 255-horse V6 as the standard motor, and the optional 4.6-liter Northstar V8 churning out a smooth 320 ponies for those who expect a little more. A five-speed automatic channels power to the rear wheels and eight-cylinder models are available with all-wheel drive for those who need extra traction come wintertime.

Finally, this Cadillac car is a technophile's dream, thanks to goodies such as a head-up display, active climate control, Bluetooth wireless cell phone connectivity and even an optional 15-speaker Bose 5.1 surround sound audio system. Defining where the 2006 Cadillac STS fits into the luxury sedan marketplace can be a difficult task. Larger than a midsize sedan yet priced low enough to compete with considerably smaller imports, the sporty new Caddy can comfortably compete with the E-Class and 5 Series in virtually every category. For the first time in a generation, GM's premium brand is ready to take on all challengers.

Cadillac gives buyers several STS models to choose from -- V6, V6 AWD, V8 and V8 AWD. Every STS sedan includes 17-inch wheels, leather seating, aluminum interior trim, eight-way power front seats, dual-zone climate control, an eight-speaker Bose sound system and OnStar. Popular options are grouped into three main packages. Depending on the model and trim, buyers can lux-out their STS with items like wood trim, a premium Bose sound system, satellite radio, a DVD entertainment and navigation system, adaptive cruise control, a head-up display and heated and ventilated front seats with memory recall. An adaptive suspension system (Magnetic Ride Control) is also available, as are larger 18-inch wheels.

There are two available engines: a 3.6-liter V6 good for 255 horsepower and 252 pound-feet of torque, and a 4.6-liter V8 that generates 320 hp and 315 lb-ft of torque. Both engines feature variable valve timing and electronic throttle control. A five-speed automatic with regular and sport shift programs comes standard with either engine. Cadillac STS buyers can also choose whether they want rear-wheel drive to maximize performance and economy, or all-wheel drive for better all-weather traction.

Stability control and four-wheel antilock disc brakes with a panic assist feature are standard. Airbags include seat-mounted side bags for front occupants and head curtain airbags spanning the first and second rows. The STS has not been crash tested.

A V8 STS is not exactly sport sedan-quick in its movements, but it can be pushed hard without losing composure. With the rear wheels providing the power, Cadillac's engineers were free to focus on the kind of precise steering feel that's nearly impossible to achieve with front-wheel drive. The result is a delicate feel through the steering wheel without a numb on-center sensation or overly aggressive assistance. The standard V6 is able to get the big sedan up to speed with surprising gusto. Unlike some of its competitors whose six-cylinder offerings provide merely adequate performance, the V6 in the STS rarely feels underpowered. Step up to the V8 and the 2006 Cadillac STS really shows its mettle.

Cadillac has been putting extra effort into interior quality and design as part of its self-proclaimed renaissance, and it shows. Panel fit and finish is top-notch, and premium materials such as eucalyptus wood trim and optional Tuscany leather really make the Cadillac STS shine. The automatic climate control system monitors interior temperatures in relation to outside conditions, and the driver can stay informed without looking down thanks to a four-color head-up display projected onto the windshield.