The Mercedes-Benz GLS-Class is the S-Class of SUVs, and this AMG GLS63 is the hot-headed performance variant. With three rows of seats, a V8 engine, mild-hybrid assist and tech for days, this big brute can do it all.

Redesigned for the 2021 model year, the AMG GLS is longer and wider than its predecessor, and the overall result is an imposing-looking SUV. AMG-specific design elements include the vertical-slat grille, huge air intakes and 21-inch wheels -- unless you opt for the outrageous 23s, as seen on my tester. You can even get the 23s in Mercedes' classic Monoblock design, which I hate, but my coworkers love. Around back, the look is finished off with a big diffuser and quad tailpipes.

The AMG GLS63 gets Mercedes' 4.0-liter twin-turbo V8, pushing out 603 horsepower and 627 pound-feet of torque. Floor it while going up an on-ramp and this leviathan will hit 80 mph well before the merge point. Mercedes-Benz says the GLS63 goes from 0 to 60 mph in 4.1 seconds, and I have no reason to doubt that claim. The V8's 48-volt mild hybrid system helps here, adding an extra 21 hp and 184 lb-ft into the mix, which not only adds acceleration boost but smooths out the action of the stop/start system, as well.

Powerful as it may be, this big gal is all about comfort. The AMG GLS soaks up any imperfections, the air suspension delivering a serene ride quality. There's lots of driver-assistance tech to help with highway commutes, too. I love the way Mercedes-Benz does adaptive cruise control and hands-on steering assist. The speed limit assist automatically decelerates if I cross into a slower speed zone, and the route-based speed adaption can adjust my speed for upcoming curves, toll booths or roundabouts. Sure, sometimes it slows down a bit too much, but I'd rather have it err on the side of safety. The steering assist responds to bends in the highway much as I would, keeping the GLS in the center of the lane without ping-ponging back and forth. The lane-change assist moves the car over when it's clear, as long as I signal appropriately.

Once off the highway and on my favorite twisty roads, I turn off the driver-assistance controls and hit that Sport Plus button. Immediately I have better throttle response, quicker shifts from the nine-speed automatic transmission, improved steering response and firmer damping settings in the air suspension.

I shouldn't be able to drive a car this big this fast, but it's all effortless. In Sport Plus the transmission downshifts on braking, upshifts quickly and the V8 emits a burble you wouldn't expect from a three-row luxury SUV. The all-wheel-drive system can throw 100% of the torque to the rear wheels and the massive 285/40/ZR23 front, 325/35/ZR23 rear Michelin Pilot Sport 4S tires provide grip for days.

The large 15.7-inch front and 14.6-inch rear disc brakes are powerful, but the GLS gets a bit squirrley under hard braking. That's not totally inappropriate, though, considering this thing weighs nearly 6,000 pounds.

And therein lies the rub. Good as the GLS63 is on a winding road, the sheer size doesn't compel me to carve canyons on the daily. Even so, I get plenty of joy from the powerful highway prowess and the way it stays flat on lazy curves. The GLS63 is still satisfying to drive.

I want to talk about configurability for a second, because there are a lot of ways to adjust this car, and frankly, it's a bit overwhelming. Independent of the main driving modes, there are dials on the steering wheel where I can adjust the air suspension to Comfort, Sport or Sport Plus. I can also put the car into manual-shifting mode and adjust the exhaust mode. I can also adjust all three of these functions from the center console.

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As for those driving modes, there are the ubiquitous Comfort, Sport, Sport Plus and Individual, but the AMG GLS adds Trail for mud or slippery conditions and Sand for when you want to take your $130,000 SUV to the dunes. Both off-road modes raise the suspension over 2 inches and give drivers the option to select their preferred levels of traction. While the AMG GLS comes with an electronic rear locker and the aforementioned off-road drive modes, those who frequently leave paved paradise will likely want to opt for one of the less-aggressive GLS-Class models. Or just get a G-Wagen.

Inside, the AMG GLS is dominated by its pair of 12.3-inch screens, one showing the reconfigurable gauge cluster, the other displaying infotainment. The MBUX system is fairly easy to use, and both Apple CarPlay and Android Auto are standard. I love the augmented reality navigation system that uses the forward-facing camera to show exactly where to turn, and it can also display addresses so I don't have to squint at the numbers on a curb. The nav system also incorporates What3words technology, which assigns a 3-meter square a unique 3-word address. It's really useful if you're trying to find someone at a carpool area or place without a specific address. Also, it's kind of cool to see what three words have been assigned to places you frequent. For example, one of my favorite off-roading spots is "upstage, stumbling, sticks." Sure, you could use a traditional latitude and longitude, but the words are often easier to remember than the numbers.

MBUX also has an AMG-specific page where drivers can record engine data, access all kinds of graphical information, spit out drag race stats, or heck, it will even navigate to the nearest race track. Similarly, an AMG performance page has information on acceleration, braking, pitch, roll and steering angle as well as an engine page with fluid temperatures and your average consumption. (I got 16.6 mpg, by the way.)

MBUX's voice recognition software is pretty good, too, understanding natural language and totally able to decipher my weird-sounding street name. The system can tune your radio station, turn on the massaging seats, even tell you a joke. A funny one, too.

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Charging is plentiful in the AMG GLS, with wireless charging, two USB-C ports in front, one in the center console, two for the second row and then two for each seat in the third row. The cargo area has a 12-volt outlet and the second row also gets a two-prong, 115-volt outlet. No phone should ever go dead in this SUV.

In addition to being techy, the interior is seriously luxurious. There are the ubiquitous heated seats, but how do heated door center panels, arm rests and center console sound? I can dig it. I'm also a fan of the heated and cooled cup holders, since I'm always down for a cold soda. The Energizing Comfort program is a bit wackadoo, altering the lighting, climate control and massaging seats to align with Mercedes-programmed Refresh, Warmth, Vitality, Enjoyment, Training or Well-Being programs. I've never come away from using this tech-for-the-sake-of-tech thinking anything but, "Well, that was weird," but it's interesting nonetheless.

I've always preferred Mercedes' interiors over its German rivals, and the GLS is no exception. There's plenty of Nappa leather, open-pore wood and I'm totally here for the center grab handles. I can do without the fake vent on the right hand side of the infotainment screen, but it's a small quibble in an otherwise excellent cabin. It's incredibly spacious, too, with 17.4 cubic feet of space behind the third row, 48.7 cubes behind the second row and 84.7 cubes when both rows are folded.

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The 2021 Mercedes-AMG GLS63 starts at $134,090 including $995 for delivery, but my tester has all kinds of options and comes out to $149,115. Personally, I don't need a $1,500 carbon-fiber engine cover and I can save $4,450 by opting for the standard 21-inch wheels instead of these 23-inch monsters. I'd probably leave the $4,550 Burmeister sound system on the table, too.

While a three-row SUV with over 600 hp may be a tough sell to us regular folk, for those that have the coin there isn't really that much in the way of competition. Both the BMW X5 M and X6 M are two-row only, as is the Porsche Cayenne Turbo S E-Hybrid (although that last one makes 670 horsepower -- yowza). You can get a supercharged V8 in a Land Rover Range Rover, but again, no third row. You'll find three rows in a Lincoln Navigator and Cadillac Escalade, but both those are limited to the mid-400s in power. Really, the closest competitor in this opulent set is the upcoming BMW Alpina XB7.

There's of course the question of why a 600-hp, three-row SUV even exists. It's not like you're going to go to the track with your kids strapped into their Recaro car seats in the back, right? Still, the AMG GLS63 is a hoot, and it exists because, well, it can. And for those who can afford it, there are many rewards to be found within.