Whether you're being forced out of a sports car by a growing family or just trying to impress the valets at your favorite hot spot, a midsize luxury sport sedan is a great place to start. And if you'd like one with a bit more excitement than the norm, the 2015 Audi S6 is an even better place to start.

Based on the less powerful Audi A6, the S6 is a four-door luxury sedan that really delivers on the promise of driving fun. Equipped with a turbocharged V8, all-wheel drive and an adjustable air suspension, the S6 is powerful, comfortable and thrilling all at once. Many of the A6's options are standard on the S6, and the interior is similar, too -- a welcome carry-over. Materials and layout are excellent, and the seats are sure to soothe you on long road trips just as easily as they'll keep you planted on a back-road sprint.

Depending on where you look, there are faster luxury midsize super sedans available, some of which even cost a bit less. The S6 competes directly with the long-time king of this class, the 2015 BMW 5 Series, which in 550i trim has a more powerful V8 than the Audi, though it doesn't feel as sharp around turns. The 2015 Jaguar XF 5.0 Supercharged is another option for the enthusiast buyer, but the Jag's interior may seem a bit outdated by comparison. Also available are the 2015 Mercedes Benz E550 and the 2015 Cadillac CTS V Sport, both of which offer prodigious power and some personality, too.

But the Audi is arguably the most rewarding to drive, and it's certainly one of the best to live with on a daily basis. If you're looking for a sedan that's lush, well-equipped, seriously fast and seriously fun from behind the wheel, the 2015 Audi S6 belongs at the top of your list.

The 2015 Audi S6 is a midsize super sport sedan that comes in a single well-equipped trim level.

Standard features include 19-inch wheels, S-specific styling elements, full LED exterior lighting (headlights, running lights and taillights), an adaptive air suspension, a sport differential, a sunroof, heated and auto-dimming side mirrors, front and rear parking sensors, a blind-spot warning system and keyless ignition and entry. Inside you'll find a head-up display, a driver information center with a 7-inch display between the gauges, Drive Select (providing adjustable settings for steering, suspension and transmission calibrations), diamond-stitched leather upholstery, eight-way power heated front sport seats (with four-way power lumbar), a power tilt-and-telescoping steering wheel, driver memory settings, four-zone automatic climate control, an auto-dimming rearview mirror, Audi's MMI system with console-mounted controls and a central 8-inch display, a navigation system, a rearview camera, Bluetooth, Audi Connect (including enhanced Web-based navigation and information services plus mobile WiFi capability) and a 14-speaker Bose audio system with a CD player, HD radio, satellite radio and iPod connectivity.

Most options for the S6 are organized into packages. The Driver Assistance package adds adaptive cruise control (with stop-and-go functionality), lane-departure warning/keeping, a 360-degree parking camera system and the Audi Pre-Sense Plus collision mitigation system. The Individual Contour Seating package features multicontour front seats with ventilation and massaging functions, front passenger memory settings, comfort rear seats and leather upholstery sans diamond stitching. The Cold Weather package adds heated rear seats and a heated steering wheel. Finally, the Black Optic package tacks on exclusive 20-inch wheels, body-color exterior mirrors (instead of the standard silver ones), a blacked-out grille and gloss-black window surrounds.

Stand-alone options include 20-inch wheels, a simulated-suede headliner, night vision assist, rear side airbags and a 15-speaker Bang & Olufsen audio system.

The all-wheel-drive S6 is powered by a twin-turbocharged 4.0-liter V8 that pumps out 420 horsepower and 406 pound-feet of torque. The transmission is a seven-speed automated manual (Audi's S tronic) that works in concert with the standard all-wheel-drive system.

According to Audi, the S6 accelerates from zero to 60 mph in just 4.5 seconds. But that's not all: The S6 also earns EPA fuel economy ratings of 20 mpg combined (17 city/27 highway). That's an exceptional combination of power and efficiency, particularly for an all-wheel-drive V8 sedan.

Standard safety equipment on the 2015 Audi S6 includes antilock disc brakes, stability control, a blind-spot warning system, front and rear parking sensors, a rearview camera, front seat side airbags, full-length side curtain airbags and front knee airbags.

Rear side airbags and a lane-departure warning/keeping system are optional, as is the Audi Pre-Sense Plus collision mitigation system, which warns the driver and automatically activates the brakes and adjusts the front seats for maximum protection if a crash is deemed imminent.

In government crash tests, the S6 received five out of five stars overall, with five stars for frontal crash protection and five stars for side crash protection. The independent Insurance Institute for Highway Safety gave the similar A6 its highest rating of "Good" in the moderate-overlap frontal-offset, side-impact and roof-strength tests. The A6's seat/head restraint design was also rated "Good" for whiplash protection in rear impacts.

Although the turbo V8's 420 horses sound like a lot, they actually put the S6 on par with more conventional sedans such as the BMW 550i, falling short of insane super sedans like the M5 and Mercedes-Benz E63. But don't get us wrong -- the S6 is still an astonishingly fast car, and the engine's refinement is about as good as it gets. Same goes for the automated manual transmission, which is equally content ripping off perfect rev-matched downshifts or just trundling around town.

On the handling front, the S6 approaches sports car territory with its quick steering and tenacious grip, yet the standard air suspension keeps the ride civilized on all surfaces. There are cars that do certain things better than the S6, but very few can match this Audi's all-around excellence.

Just a few minutes behind the wheel of a 2015 S6 should convince you that this is one of the nicest interiors around. Highlights include a handsome dashboard layout, top-notch materials quality and solid fit and finish. The standard MMI controls entertainment, communication and navigation functions via a dash-mounted pop-up screen and a knob and buttons on the center console. The system boasts logical menus, crisp graphics and a touchpad to increase functionality, although we still prefer BMW's iDrive or Mercedes' COMAND for overall ease of use.

The S6 also features the Audi Connect telematics suite, which includes in-car WiFi, Google Earth data for the navigation system and simplified Google search functionality for points of interest. The mobile WiFi proves very handy if you need to get some work done on the road and there's no Internet café to be found. The Google Earth feature is a mixed bag, however, as it's a bit harder to understand at a glance than a conventional map.

Whether you keep the standard sport seats or opt for the multicontour comfort seats, you'll enjoy excellent support during long trips and spirited back-road runs alike. As for the S6's trunk, its 14.1-cubic-foot volume is a little below average for this segment, but it has a useful rear seatback that folds down in a 60/40 split and offers a pass-through feature.