The S4 will officially hit somewhere north of 145 mph. A radar detector ought to be standard equipment on this car simply because it is so tempting to hit the gas and go flying. You'll reach 60 mph in less than 6 sec from a standing start, and only with great restraint will most drivers be willing to stop there.

Interestingly, the S4 doesn't look like a hot car. It has the appearance of a handsome sporty compact. As you might expect from its name, the car is based on the Audi A4 platform and seems to have combined the best parts of the A4 with a luxurious interior and a big engine.

A six-speed Tiptronic transmission is standard. It operates as an automatic but lets drivers up or downshift with a flick of the wrist on the console shifter, or, with the touch of finger on a paddle shifter built into the steering column.

The S4 is also clearly designed for those who appreciate cars that handle well. High spring rates, antiroll bars front and back, quick steering, and sure braking, along with all-wheel-drive let it cling to corners and man-handle the curviest roads. You might expect a car with such a firm ride and precision through slaloms to be race-car harsh over potholes. Big surprise: The S4 smoothes out potholes, reminding occupants it is indeed a luxury car.

The luxury car persona extends into the passenger compartment. Dual-zone climate controls feature dust and pollen filters; power windows have pinch protection; leather upholstery covers the interior and on the steering wheel, set off by grey Birchwood trim. Front-seat occupants sit in 12-way power Recaro sport seats. There is a headlight washer system concealed in the front and heaters in the outside mirrors.

We had precious few gripes with our S4 test vehicle. Leg room in the back is a little tight. And controls on the entertainment system are not intuitive so buyers should expect a learning curve.

The base price for the S4 Quattro (AWD) is $47,300. There is also an Avant station wagon version for buyers seeking more room. Our test vehicle carried options that included a $450 metallic paint job, a $2,000 premium package covering frills such as a power sunroof, auto-dimming mirrors, seat and mirror memory, and sensors for rain and darkness. A navigation system added $1,950 and Sirius Satellite radio and premium sound another $1,000. Heated front and rear seats ($575) and 18-in. cast alloy wheels ($450) rounded out the options.

Potential buyers should note that they will also pay a $1,300 gas-guzzler tax. The S4 is rated to get 15 mpg in the city and 23 mpg on the highway. (Our only comment here is that people who buy cars like this don't do so for the gas mileage.) The total for the test car came to $55,745.

Finally, Audi figures the S4 competes against cars such as the BMW M3 and Mercedes-Benz C32 AMG. Neither of these carry a V8, and we have a hard time believing they would be as fun to drive as the S4.

—Lee Teschler