A V8-powered GLC seems to be in the works.

What makes an already-excellent compact luxury crossover even better to drive? Why, the addition of a biturbo V8, of course.

That's what spies claim to have caught testing in Germany, citing reports of a "roaring" V8 emanating from this Mercedes-Benz GLC mule.

If they're correct (and chances are that's the case), we're looking at the new Mercedes-AMG GLC63--based on successor to the old GLK.

There's not much to see on this early testbed, but big wheels, big brakes and some revised bodywork appear to be the name of the game. What really sets the "63" models apart from their "43" siblings is under the hood.

If it follows the recent pattern, we expect the Mercedes-AMG GLC63's twin-turbocharged V8 will boast roughly 475 horsepower in base models and more than 500 in the hopped-up GLC63 S model.

Stay tuned for more information, as we expect details of the Mercedes-AMG GLC63 to emerge after the GLC43 model arrives in early 2017.