Not long ago, coupe-styled sedans such as the BMW 6 Series Gran Coupe were an oddity in the automotive world. But in 2014, most European automakers sell at least one, if not two or three. Although it's part of the BMW 6 Series line in name, the 2014 6 Series Gran Coupe is more of a low-roofed version of the 5 Series sedan with a few more curves and contours thrown in for good measure.

In fact, the 2014 BMW 6 Series Gran Coupe and 5 Series sedan share all their major dimensions. Predictably, though, the sleeker Gran Coupe has less headroom. It also has a less practical seating layout, as its center console extends into the backseat, limiting the usefulness of the rear center seat. Then again, if you're looking at the Gran Coupe as an alternative to the two-door 6 Series coupe, it starts looking pretty rational. With 4.5 inches of added length between its wheels and two extra doors, the Gran Coupe has a bigger rear seat and easier access to it.

Engine choices range from sensible to decadent. The base 640i is powered by a strong and fuel-efficient 315-horsepower, turbocharged inline six-cylinder engine, while the 650i features a 445-hp turbocharged V8 that's less frugal but a great deal more enjoyable. Both come mated to an eight-speed automatic transmission with paddle shifters. And for 2014, both are available with all-wheel drive, potentially making your 6 Series Gran Coupe quite practical for year-round driving.

However, the 640i Gran Coupe costs considerably more than a comparably equipped 535i sedan, and is even a few bucks more than the base 740i -- both of which are motivated by a version of the same six-cylinder engine. Meanwhile, the V8-powered 650i is even more expensive, and any of the 2014 BMW 6 Series Gran Coupe models can go into the six-figure range if you go heavy on the extras.

Competitors include the Audi A7 and S7, Mercedes-Benz CLS550 and Porsche Panamera . All provide satisfying driving dynamics, ample luxury amenities and plenty of style, and often for less money. Is the 2014 BMW 6 Series Gran Coupe worth the premium? On paper, it may be a tough sell. However, in the metal, there's no denying it becomes a far more emotional proposition.

The 2014 BMW 6 Series Gran Coupe is a four-door sedan with coupelike styling. Four trims are offered: 640i, 640i xDrive, 650i and 650i xDrive.

Standard on the 640i Gran Coupe are 18-inch wheels, adaptive suspension dampers, adaptive xenon headlights, LED foglamps, automatic wipers, parking sensors, power-folding mirrors, keyless ignition/entry, a sunroof, six-way power front seats (with four-way lumbar adjustments and memory functions), heated front seats, leather upholstery, a power tilt-and-telescoping steering wheel, auto-dimming mirrors, dual-zone automatic climate control, cruise control and a rearview camera. Electronic features include Bluetooth; a navigation system; real-time traffic information; voice controls; satellite radio with a one-year subscription; the iDrive electronics interface with smartphone app integration; and a nine-speaker sound system with a CD player, HD radio, a USB/iPod interface and an auxiliary audio jack.

The 650i features a V8 engine in place of the 640i's six-cylinder and adds 19-inch multispoke wheels, 16-way power multicontour seats (with four-way lumbar adjustment), a premium sound system and telematics concierge services. The 640i xDrive and 650i xDrive models also have all-wheel drive.

Several option packages are available. The Driver Assistance package features side/top-view cameras, blind-spot detection, lane-departure warning and speed-limit information. The Cold Weather package provides heated rear seats and a heated steering wheel, and the Lighting package adds full LED headlamps and automatic high beams.

The Executive package adds soft-close doors, a head-up display, four-zone climate control and ventilated front seats, telematics concierge services and a premium audio system for the 640i. For the 650i, it also brings a power rear sunshade, manual rear window shades, contrast stitching, ceramic controls and a leather-topped instrument cluster.

The M Sport package includes 19- or 20-inch double-spoke wheels, lower-body aero styling, a unique three-spoke steering wheel, a faux-suede headliner and a higher (155 mph) top speed limiter. The Individual Composition package includes 19- or 20-inch wheels, LED headlamps, darkened window trim, upgraded leather upholstery, a faux-suede headliner, unique cabin accents (piano black, Sycamore wood or White Ash wood) and the availability of unique, extra-cost exterior paint colors.

Individual options include adaptive suspension stabilizer bars (known as Adaptive Drive), active steering (not available on xDrive models), a night-vision camera, adaptive cruise control, extended leather upholstery, automated parallel-parking assist and a 16-speaker Bang & Olufsen surround-sound audio system. Many of the package features are available as individual options as well.

Powering the 2014 BMW 640i Gran Coupe is a turbocharged 3.0-liter inline six-cylinder engine that makes 315 hp and 330 pound-feet of torque. Fuel economy estimates for the rear-wheel-drive 640i stand at 24 mpg combined (20 mpg city/30 mpg highway); the 640i xDrive achieves 23 mpg combined (20 mpg city/29 mpg highway). In Edmunds instrumented testing, we recorded a 5.7-second 0-60 time in the rear-drive 640i Gran Coupe, which is average for this class of car.

The 650i Gran Coupe packs a turbocharged 4.4-liter V8 that generates 445 hp and 480 lb-ft of torque.  Fuel economy drops significantly with the V8, to 20 mpg combined (17 mpg city/25 mpg highway) for the rear-drive 650i and 19 mpg combined (16 mpg city/24 mpg highway) for the xDrive 650i Gran Coupe.  In our testing, a rear-drive 650i Gran Coupe hit 60 mph in 5.2 seconds. That's quick, but the CLS550 is quicker.

Standard safety equipment includes antilock brakes with advanced standby and drying features, traction and stability control, front-seat side airbags, front knee airbags and active front head restraints. Also standard are front and rear parking sensors; a rearview camera and the BMW Assist emergency communications system, which provides automatic crash notification, stolen vehicle recovery and on-demand roadside assistance.

The optional Driver Assistance package features enhanced side/top-view camera displays, blind-spot detection and a lane-departure warning system. A night vision system with pedestrian detection is also available, as is an automated parking system (BMW Parking Assistant).

In Edmunds brake testing, the 640i Gran Coupe came to a smooth stop from 60 mph in a short 110 feet, very impressive for a 4,300-pound luxury car. The 650i stopped in 114 feet.

Its acceleration numbers may be nothing special, but the 2014 BMW 640i Gran Coupe certainly feels quick in everyday driving. Its turbocharged inline-6 picks up steam rapidly as the revs climb, and the automatic transmission is on point as well, providing quick and timely downshifts. The 650i's turbocharged V8 feels downright decadent in the power department, as it unleashes a seemingly endless flow of thrust, moving the big sedan down the road with authority.

Like other BMWs, the 6 Series Gran Coupe has that unflappable Germanic feel at high speeds, yet somehow manages to feel smaller than it really is when you drive it around turns. All the while, the ride quality is firm, yet suitably luxurious for a car of this price and level of prestige.

That said, we're not so enthusiastic about how the 6 Series Gran Coupe feels when equipped with the optional active steering and active stabilizer bars (Adaptive Drive). These bits of tech lend a somewhat unnatural feel when hustling the car along a back road. In particular, the steering lacks the company's trademark road feel, while the sophisticated stabilizer bars are actually too effective, decreasing body roll to the point that you no longer have a sense of how hard you're pushing the car.

The intimate cabin of the Gran Coupe is decidedly driver-focused and is trimmed with top-quality materials and standard leather upholstery. The appearance of the cabin ranges from simple and elegant to edgy and avant-garde, depending on the color, wood and other trim options you select.

The front seats are superbly comfortable and are set low within the cabin, reinforcing the car's sporty feel. While rear seat passengers fare better than in the two-door 6 Series models, the backseat feels considerably more confining than in the 5 Series and the lower roof line reduces headroom. The so-called "+1" center rear seating position is useful only for children on very short trips, as the extended center console eats up all of the legroom.

As with other 6 Series models, the 2014 Gran Coupe also features BMW's improved iDrive control interface with 3-D graphics and a wide, 10.2-inch screen. You'll use iDrive to manage entertainment, climate control, navigation and phone functions, as well as various vehicle settings. There's a lot of functionality here, and although we advise you to take some time to study the various features before you hit the road, iDrive is notable for its sharp graphics, fast processing times and logical menu structure. New to the system for 2014 are enhanced split-screen displays, 3-D city model navigation, dictation features, text messaging and dual-phone pairing.

Trunk capacity is just 13.0 cubic feet and the trunk lift-over is rather high, but added practicality comes in the form of split-folding rear seats and an armrest pass-through.