The four-door coupe niche is a small one, but some people love the idea, and it seems as if it is slowly starting to take off. BMW has the 4 Series and 6 Series Gran Coupe here in the U.S. Maserati has the Quattroporte, Porsche has the Panamera, and Audi is about the drop the A5 and S5 Sportback models into the market for 2018. Mercedes already has the CLS Coupe, which – in the right trim – could be considered a competitor to the aforementioned models. But now it looks like the German brand may be fielding another competitor for this niche. It’s a four-door concept of the Mercedes-AMG GT, and it’s set to debut at the 2017 Geneva Motor Show.