The S4 is the latest in Audi’s expansive A4 line. At the bottom is the $25,970 A4 sedan that’s powered by a turbocharged 170-hp four-cylinder engine. Until this S4 cabriolet debuted, the top model was the S4 sedan (the “S” prefix denotes the hot-rod model), a $48,070 four-door with a 340-hp V-8 and standard six-speed manual transmission. In between, there are three body styles—sedan, wagon, and convertible—and a variety of engines and transmissions. The Quattro four-wheel-drive system is available or standard on all models.

The S4 sedan is one of our sweethearts. It won a comparison test in May 2003 Compact (“Adrenaline-Delivery Systems”) and snagged a spot on this year’s 10Best Cars list. Its combination of burly V-8 power, tautly beautiful sheetmetal, and four-wheel-drive sure-footedness is unbeatable in this segment of the car market. We all expected the droptop version to be just as sweet and, well, basically, it is.

The most notable difference for the 2007 convertible model, which Audi calls the S4 Cabriolet, is the restyled front end with its larger trapezoidal grille. At the expense of some rear-seat space, the S4 Cabriolet features an insulated, power-operated fabric roof with a glass rear window that can be raised or lowered while driving at speeds up to 19 mph. An optional acoustic roof makes use of denser fabrics to further reduce road noise. Audi claims a Cabriolet fitted with the optional headliner is as quiet as the sedan, even at highway speeds. The convertible also features an occupant-protection system in which two protective bars located behind the rear seats pop up within milliseconds if sensors detect the vehicle is about to roll over.

All S4 models come with a 4.2-liter V8 engine that generates 340 hp and is capable of taking the S4 to 60 mph in just 5.3 seconds with the standard six-speed manual transmission. A six-speed Tiptronic automatic transmission that affords manual gear selection is optional.

You’ll pay at the pump for all that power, with estimated fuel economy of 15 mpg city/21 mpg highway with the manual, and 15 mpg city/23 mpg highway with the automatic. Given its poor gas mileage, the S4 is subject to a federal gas-guzzler tax.

Ever since BMW developed the idea of a special line of up-engined production cars with its 1986 BMW M3, an increasing number of manufacturers — Audi, Chrysler, Ford, Mercedes-Benz and others — have bought into the concept. Audi’s high-performance line includes the S series of sedans and wagons, plus even more hot-rodded RS models. The 340-hp S version of the base A4 is the newest of them (also available in a super-special 420-hp RS 4 version).

Some might wonder whether the world needs a station wagon with sports-car performance and comparatively harsh ride characteristics, but others will find great value in such utility, which even includes quattro all-wheel drive. Why own a performance car, an SUV and a wagon when you can have all three in one?

Including the gas tax, an S4 will cost you $13,260 more than the next-level-down A4 Avant, the 3.2-liter V6 quattro, which is a substantial premium to pay for 85 hp more, a less-efficient engine, a few minor styling cues to set the S4 slightly apart, sport seats and a stiffer suspension. Other than that, all optional S4 equipment is available on the A4 as well.