When the Mercedes-Benz CLS was launched in 2004, it created an entirely new segment, which the brand called a "four-door coupe." The CLS was all about style: Based on the E-class sedan, it featured sleek, sensual lines at the price of practicality and its own distinct dashboard.

The idea spread like wildfire. Audi derived the A7 from its A6, while Volkswagen conceived the CC as a Passat variation. Like the CLS, they were slightly more expensive than the models they were based on. Then BMW took the cake with the 6-series Gran Coupe, which shared its architecture with the 5-series sedan but was priced well into 7-series territory. Benz’s second-gen CLS, on the other hand, gained a station wagon version (dubbed "Shooting Brake") in some markets, but its interior was downgraded to E-class level. Meanwhile, Porsche’s whale-like Panamera followed the four-door coupe format without even bothering with the more traditional squared-off sedan version. It has become much easier on the eyes in its second iteration.

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Now Daimler has bifurcated its four-door coupe offerings. Almost simultaneously, the company launched its third-generation CLS and the new AMG GT 4-Door.

In Europe, the new CLS lineup stretches from a four-cylinder diesel through six-cylinder gasoline and diesel models, topping out with the Mercedes-AMG CLS53, which is powered by a turbocharged and supercharged 3.0-liter inline-six with a 48-volt system that makes 429 horsepower. The latter overlaps with the AMG GT 4-Door lineup that begins with a GT53 featuring the same powertrain. Above that, Mercedes-AMG offers its new four-portal coupe in V-8–powered GT63 and GT63 S versions, with 577 and 630 horsepower, respectively.

While its model designation suggests it is a derivative of the AMG GT sports car, the GT 4-Door is actually constructed on the E-class platform just like the CLS. A four-door version of the actual GT, a car that is closely related to the defunct SLS supercar, was never an option. "As an engineer, I realize at first glance that this approach wouldn’t work. You need certain spaciousness in the rear compartment, but not at the expense of the sporting character," says AMG chief Tobias Moers.

Building the GT 4-Door atop the E-class platform turns it into a more formidable competitor for the Panamera, where a version based on the two-door GT’s hardware would have resulted in something more like the Aston Martin Rapide, which is to say it would be a vehicle hampered by packaging issues and a diminutive cabin.

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But an E-class is not always a mere E-class: While the AMG CLS53 is built upon the regular-width CLS and E-class architecture, the GT 4-Door, even in its entry-level iteration, is more closely related to the AMG E63 with its performance chassis. (In fact, the GT 4-Door is more closely related to the E63 wagon than the sedan.) Still, it’s not identical. "The four-door GT features the AMG-specific rear frame with modified kinematics," says Moers, adding, "the front axle is different as well." The result: "Even when compared with the AMG E63, we are speaking of another dimension."

The engineering process is different, too. While the CLS went through the usual steps of a new Mercedes-Benz model, the AMG GT 4-Door was a much tighter project, designed and engineered in close cooperation between Tobias Moers and chief designer Gorden Wagener.

The interiors differ significantly. While the CLS interior is taken almost directly from the E-class, this only pertains to the upper half in the GT 4-Door. The center console is specific to the model, wider and elevated with a central section modeled after a large NACA air duct that features new touch-capacitive buttons. "It could be an inspiration for a facelift of the (two-door) GT," says Moers.

A diesel model like that Mercedes-Benz offers in the CLS in Europe also goes against AMG’s current philosophy. "A diesel version of the four-door GT is not planned," Moers declared, adding that, "for AMG, the future is electrified gasoline powertrains. And he whets our appetite by revealing that "for a future hybrid variant of the GT, look at the 805-horsepower concept of 2017 for inspiration."

For now, the AMG GT53 picks up neatly where the AMG CLS53 leaves off. In terms of design, the two will never be confused; where the CLS emphasizes smooth lines and an elegant demeanor, the AMG GT 4-Door oozes brutality and picks up cues from the two-door model at every opportunity.

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Nonetheless, Daimler is wary of the product overlap, and this concern is illustrated by some tweaking of the lineup. Whereas the second-generation CLS range included an AMG 63 version, that most-extreme offering won’t get a successor. The CLS Shooting Brake is gone, too, having been deemed too similar to the GT 4-Door with its rear liftgate. And the future of the CLS beyond this model generation? That’s an open question. Says Moers: "Whether the four-door GT and the CLS will be consolidated into one model line will be decided at a later point; it is a question pertaining to the next platform."

Meanwhile, pricing for both models is still undeclared, but it’s safe to assume that the GT will command a significant premium over the CLS. Competitors are also expanding their four-door coupe offerings: BMW is calling its replacement for its 6-series Gran Coupe the 8-series, even as it already has the 6-series Gran Turismo to replace the former 5-series model.

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