2000 Audi S4

Perhaps the best thing about this nearly decadelong U.S. auto boom is the wealth of specialty or niche vehicles that now populate the market.

It has allowed automakers to create high-performance roadsters and sport-utilities, racing-inspired versions of coupes and sedans and even minivans stuffed with all manner of video games and entertainment systems.

And, this week, it has brought us the Audi S4.

This is a souped-up version of Audi’s entry-level A4 sedan, which is a perfectly good $25,000-to-$30,000 car. In its S4 iteration, which sells for about $40,000, it’s transformed into magic on wheels.

The good stuff starts with a 2.7-liter V-6 engine equipped with two small turbochargers. It generates up to 250 horsepower and plentiful torque at relatively low RPMs. Coupled with a six-speed manual transmission — a five-speed automatic with Tiptronic is a no-cost option — the S4 races from zero to 60 mph in less than six seconds.

Compare those numbers with those produced by the normal V-6-equipped A4 — 190 horsepower and a 7.2-second zero-to-60 time — and it’s easy to contemplate the performance upgrade on the S4.

Not that the engine was the only upgrade on the German-built sports sedan. The suspension is beefed up with much use of aluminum. The brakes are stronger, too.

The total package is one that impresses with its unity and sophistication. There’s plenty of speed, obviously, but it’s the balance that makes the S4 most attractive.

On the outside, the S4 differs subtly from a base A4. Besides the S4 badging, the car has a lower stance and wider air intake ports up front. The big tires (17 inchers) and the clear glass covers over the xenon high-intensity lights also are eye-catchers.

Imola yellow and Nogara blue, two only-S4 paint colors, are available, in addition to the usual palette of black, silver, green, blue and two shades of red.

To the person who loves to drive hard and fast, the S4 will become the ultimate stealth car where the performance potential inside remains neatly hidden under a conservative exterior.

In the cabin, the car comes with the requisite leather and wood combination. On our test car, however, the S4 came with leather combined with a special suede upholstery called Alcantara and a silver aluminum trim instead of wood for a more distinctive appearance. The rear seat space approximates that in the A4, which means it’s only adequate when it comes to roominess for the legs of a full-size adult.

Our tester also included Audi’s new navigation system, a $1,100 option. Unlike other cars now on the market, this one doesn’t include a dash-mounted monitor. Instead, a driver uses buttons between the front seats to give inputs, and the directions and turn arrows are then displayed in red on the instrument panel. Audi’s reasoning is that its system is safer to use while driving. I found it accurate but manipulating the knobs was a bit of a headache.

Like other Audis these days, the S4 is full of safety equipment, including dual front and side air bags, anti-lock brakes and the venerable Quattro all-wheel-drive system that now comes with a new traction-control component.

All told, the S4 moves Audi further in the direction of competing directly with BMW and Mercedes-Benz. Up to now, Audi has offered American buyers a nice stepping-stone lineup of sedans and wagons (A4, A6, A8) to compete with BMW’s 3-, 5- and 7-Series and Mercedes’ C-, E-and S-Class cars. Now, just as BMW offers exclusive M-Series vehicles and Mercedes has AMG-built specialty cars, Audi has the S4.

What we drove: 2000 Audi S4 2.7T, a sport sedan with a 250-horsepower, twin-turbocharged 2.7-liter V-6 engine, a six-speed manual transmission and full-time all-wheel-drive.

Base price: $37,900 Price as tested (includes options and delivery charge): $41,925

0-60 mph time: 5.9 seconds

Top speed: 143 mph

Curb weight: 3,593 pounds

Length: 176.5 inches

Turning circle (curb to curb): 37.4 feet

Standard features: Automatic transmission with Tiptronic; anti-lock brakes; automatic air conditioning with filter; 17-inch performance tires; sport suspension; tilt, telescopic steering; heatable windshield washer nozzles; Xenon headlights; two front and one rear fog lights; power windows, locks and mirrors; cruise control; power front seats; 60/40 split, folding rear seat; silk Nappa leather upholstery; maplewood trim; trip computer; alarm system; AM/FM stereo with cassette and one-disc in-dash CD player; dual front and side air bags.

Options on test vehicle: Six-speed manual transmission; convenience package with sunroof, auto-dimming mirrors and HomeLink transmitter; sport interior package; upgraded sound system with 6-disc CD changer; Audi navigation system. EPA figures: 17 mpg (city); 24 mpg (highway)