Famed BMW tuner Alpina has gotten its hands on the four-door version of the BMW 6 Series to create its latest performance model, the BMW Alpina B6 xDrive Gran Coupe. This 540-hp sports sedan costs just $1000 more than a BMW M6 Gran Coupe but offers a higher level of performance thanks to Alpina's extensive powertrain and chassis upgrades.

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Alpina's version of the same 4.4-liter twin-turbocharged V-8 engine that's available in the BMW 650i and M6 produces a lofty 540 hp and 540 lb-ft of torque. That's 95 hp more than in the 650i and only 20 hp less than in the M6 Gran Coupe. Whereas the M6 is only available with rear-wheel drive, though, the Alpina B6 comes standard with BMW's xDrive all-wheel-drive system. This makes for quicker acceleration, as Alpina says the B6 Gran Coupe makes it from 0-60 mph in 3.7 seconds compared with 4.1 seconds for the BMW M6 Gran Coupe. The Alpina B6 Gran Coupe also lords over the M6 Gran Coupe with its impressive top speed of 198 mph, mostly thanks to the fact that it's not fitted with a 155-mph electronic limiter like the M6. To scrub off all this speed, the B6 is outfitted with 14.7-inch front brake rotors and 13.6-inch rears, both of which are cooled by NACA ducts at the front of the car's underbody.

The BMW Alpina B6 xDrive Gran Coupe is also fitted with various appearance upgrades to set it apart from standard Gran Coupe models. The 20-inch, 21-spoke Alpina Classic wheels are similar to those found on the larger, 7 Series-basedAlpina B7, as is the deep blue color shown here (other colors are also available). Otherwise, the B6 Gran Coupe also gains aerodynamic elements like a front splitter and apron and a rear spoiler which give this sport sedan a smoothed-over appearance. On the inside, the Alpina B6 Gran Coupe is fitted with numerous Alpina logos along with special leather accents and either Myrtle wood or piano black trim finishes.

The 2015 BMW Alpina B6 xDrive Gran Coupe is a special-order model that will be available in the U.S. in April at a cost of $118,225 including destination. Like other Alpina models, it carries a factory BMW warranty and is sold through BMW dealerships. Stay tuned for the U.S. debut of this sports sedan next month at the 2014 New York auto show.