Long revered for its stoic sedans and wagons, Mercedes-Benz bunched the underpants of more than one purist when it introduced the ML-class SUV in the late 1990s. (True, the *Geländewagen, or G-wagen, had *been around for decades, but that purpose-built, low-volume vehicle was engineered for military use before being forced into consumer service by well-heeled status-seekers.) While the cognoscenti were still busy sorting out their undergarments, Mercedes launched the ML55 AMG, a hot-rod version of the then-new SUV prepped by AMG, its longtime speed merchant. That model is the distant ancestor of the 2016 Mercedes-AMG GLE63 S tested here. **Names and Numbers ** Known internally as the W166, the current GLE-class is the third generation of the automaker’s mid-size SUV. With arrival of the 2016 model year, the “ML” moniker was ditched in favor of “GLE” as part of a brand-wide effort to make its product-naming scheme more logical. (2016 also brought the debut of the similarly named GLE coupe, which did little to aid the quest of tidying up the brand’s nomenclature.) Regardless of the lettering on its tail, the Mercedes-AMG GLE63 S is an SUV that is not easily forgotten Powered by a twin-turbo V-8 producing 577 horsepower and 561 lb-ft of torque (that’s 27 hp and 45 lb-ft more than the non-S Mercedes-AMG GLE63), our GLE63 S decimated the quarter-mile in just 12.2 seconds with a trap speed of 115 mph; the blast to 60 mph was over in 3.8 seconds. Engine output is funneled obediently through a seven-speed automatic transmission, which delivers full-throttle upshifts with brutal decisiveness, particularly in Sport+ mode. And the powertrain sounds positively sinister in operation. Given the constant allure of all the readily available thrust, we can’t really fault the GLE63 S for returning a very Sierra Club–unfriendly observed fuel-economy figure of 14 mpg. We were just happy to land between the EPA’s 13-mpg city and 17-mpg highway ratings Michelin Latitude Sport 295/35 tires wrapping 21-inch wheels not only make the most of every iota of the V-8’sbut also assist in hauling the GLE63 S to a stop from 70 mph in 166 feet, bettering by 13 feet the number posted by the 2015 Land Rover Range Rover Sport SVR but trailing by 10 feet the last Porsche Cayenne Turbo S we tested. Crucially, the brake pedal is easy to modulate, and repeated stops produced no fade. Mercedes tells us the chassis tuning was revised for 2016; paired with the massive Michelins, the GLE63 circled our skidpad at 0.95 g. While such feats of automotive derring-do have become almost— *almost*—routine in the forced-induction, dynamic-suspension world in which we now live, it’s important to remember that we’re talking about a 2.5-ton-plus SUV (tipping our scales at 5315 pounds). Still, its ability to post some mind-bending numbers doesn’t replace the quick responses and tactile feedback that makes driving a smaller, lighter performance car so appealing The model’s 2016 refresh brings new front fenders, fascia, and head- and taillamps that offer subtle refinements of the previous versions. Likewise, the interior trades on styling cues of the previous generation; it’s a warm and familiar feeling, but then the wealthy aren’t known for being content with last year’s, uh, anything **What Price Performance What premium, exactly, does the privilege of wearing the “S” appellation on the rump of a GLE63 command? Based on the $108,185 base price of our GLE63 S, that answer would be $7150, barely enough cash to strain the seams of the average buyer’s hand-tooled bison-spleen pocketbook—or whatever device those who drop more than $100K on 12-second SUVs keep their money in. Of course, exiting a Mercedes-Benz dealership without checking some options boxes is akin to visiting Stuttgart without trying the schnitzel—not gonna happen Our tester was loaded with niceties, most notably an AMG Performance exhaust ($625), a panoramic sunroof ($1090), a Bang and Olufsen audio system ($5400), multicontour front seats with massage ($1100), three-zone climate control ($790), and other trinkets. More than three grand’s worth of options were installed solely for the benefit of the second-row passengers:entertainment ($1950), rear heated seats and climate-control panel ($620), and a rear convenience package with pass-through armrest and manual window shades ($490). Finally, the driver-assistance package ($1950), which includes the usual safety features, and Cardinal Red Metallic exterior paint ($360) brought the final tally to a not-insubstantial $123,835 In an era when $100,000-plus über-SUVs like the Bentley Bentayga, BMW X5M, and Porsche Cayenne Turbo S have become almost commonplace, the lines between practicality and absurdity have been blurred. For those who revel in populating that slice of reality, the GLE63 S represents a compelling choice—whatever Mercedes chooses to call it.