By Barbara & Bill Schaffer

Peripheral to the throng of high-horsepower vehicles now on the market producing 400, 500, 600 and 700 horsepower, there is a group of performance models with a more moderate range of horsepower that we think are the sweet spot in the performance car lineup. These cars, mostly by luxury brands, that are taking advantage of turbocharging and supercharging four- and six-cylinder engines which generally produce from the low 300 to 400 horsepower. The result is a group cars and SUVs that are refined, extremely fun to drive and somewhat economical to operate.

A good example of a car in this category is the upper level model of the Audi A4 lineup, the Audi S4. The turbocharged four-cylinder engine in the A4 has long been one of our favorites, but we admit the supercharged V-6 in the S4 improves on an already impressive sedan.

The 333-hp 3.0-liter supercharged V-6 in the S4 is a perfect application for the car. It has the power to make a 0 to 60 mph run in 4.9 seconds and go to a top speed limited to 155 mph. The EPA rates the S4 fuel economy at 21 mpg city, 28 mpg highway and 21 mpg combined. We averaged 23.6 mpg during the week we were driving it.

The supercharged engine is available with Audi?s excellent seven-speed S tronic dual-clutch automatic transmission, which includes steering wheel-mounted shift paddles for people like us who prefer the ability to control the speed with gearing and not just brakes. For the purists, the S4 is also available with a six-speed manual transmission. And like about 80 percent of the Audi?s sold in the U.S. it has quattro all-wheel drive. Our test car also had the optional ($1,100) rear sport differential which distributes the power back and forth between the rear wheels for better cornering.

The S4 has a system that allows the driver to select vehicle characteristics to change driving dynamics using a button on the center console. It can be set at Comfort, Auto, Dynamic or Individual based on the conditions the driver is expecting.

The result is a beautiful combination of refined performance and handling that makes this car a pleasure to drive under any conditions and on any roads. Living in the Northwest, we especially appreciate the all-wheel drive on the wet and slippery road surfaces we often deal with.The A4/S4 got a facelift in 2012 and current model year changes are limited to minor tweaks, wheel changes and adjustments to the equipment offerings. Still the car has a classic contemporary design that ages well. We particularly like the LED daytime running lights and the standard Xenon headlights which light up the road quite nicely.

The S4 interior on our 2014 model year test car was attractive and business-like, without a lot of superfluous wood or carbon fiber d?cor ? those features are optional however. The accents on our test car were aluminum trims around the instrument pods, the vents and on the center console. The dark-colored soft vinyl trims don?t have the fancy French stitching, but the excellent organization and ergonomics makes up for lack of bling. Center console real estate is used for important features like the shifter, electronic parking brake switch, start button and the MMI control buttons along with handy drink holders and storage areas.

The MMI Navigation system is not the most user-friendly system we?ve used, but it?s better than most and quite intuitive with its large control knob and buttons that switch the screen directly to different functions — navigation, audio, etc. All the controls are comfortably placed for ease of operation. We imagine it won?t require taking your eyes off the road, after you?ve used the system for a few weeks. It?s also convenient for a front seat passenger to use, to assist the driver. For those silver-tongue drivers it also responds to audio commands.

Available features on the 2015 Audi S4 quattro are a technology package ($2,900) which adds the navigation, blind sport warning, parking system, rear camera, entertainment upgrades and Audi connect?. Audi connect is an award-winning infotainment system which allows up to eight wireless devices to connect to the Internet through an internal Wi-Fi system. The Audi navigation system has available Google Earth? maps to show the routes superimposed over an actual photographic image of the terrain.

The 2015 Audi S4 is offered in two trim levels, Premium Plus and Prestige, both with the supercharged V-6 engine and quattro. The Premium Plus with six-speed manual transmission is priced at $48,400 and the Prestige is $54,300. The seven-speed automatic transmission adds $1,400 to either model. With all the available options, the Prestige pricing tops out just over $65,000.The Audi S4 is one of those cars we?d like to keep in our garage. It looks good, is a nice size for two people and occasional passengers, it?s comfortable, has all the latest technologies and is especially fun to drive.