Downsizing strikes again! Mercedes-AMG has unveiled the new GLC 43 and GLC 63 S E Performance, both of which rely on a small 2.0-litre, four-cylinder engine. It's the same longitudinally mounted M139l installed in the latest C63 saloon and estate, as well as in the SL 43 roadster. In its transverse configuration (M139), it powers AMG's spicy "45" compact cars as well as the recently launched base version of the Lotus Emira.

The crossovers share a good chunk of this engine, including the electric exhaust gas turbocharger found in the base SL as well. Eschewing the 3.0-litre V6 of its predecessor, the latest GLC 43 boasts 416 bhp (310 kilowatts) and 500 Newton-metres (369 pound-feet). It's an increase of 14 bhp over the latest C43 models whilst having the same amount of torque. Compared to the old GLC 43, you get an additional 31 bhp but lose 20 Nm (15 lb-ft). However, the new AMG Lite version has a belt-driven starter generator serving as a mild-hybrid setup with a temporary boost of 14 bhp (10 kW) and 150 Nm (110 lb-ft).

Gallery: Mercedes-AMG GLC43 (European Model)

As for the top dog, the GLC 63 S E Performance has the ICE dialled to a massive 469 bhp (350 kW), making it the most powerful four-cylinder engine ever installed on a road-going car. You get 545 Nm (402 lb-ft) of torque just from the petrol unit, and it’s all thanks to a "significantly larger" turbocharger compared to the engine found in the GLC 43. The ICE works with a rear-mounted electric motor delivering an extra 201 bhp (150 kW) and 320 Nm (236 lb-ft).

With the power of the two combined, the range-topping GLC offers a colossal output (for a crossover of this size) of 671 bhp (500 kW) and 1,020 Nm (752 lb-ft) to match the C63 models. Compared to the old V8-powered GLC 63 S, you have an additional 168 bhp and 320 Nm (236 lb-ft). Of course, power isn’t everything as these latest AMG GLCs are quite porky, tipping the scales at 1,975 kilograms (4,345 pounds) for the 43 model and a hefty 2,310 kg (5,092 lbs) for the 63 S E Performance, with both figures representative of the Euro-spec models.

As far as performance is concerned, Mercedes claims the GLC 43 needs 4.8 seconds to go from zero to 62 mph (100 km/h) before topping out at an electronically governed 155 mph (250 km/h). The GLC 63 S E Performance cuts the sprint time to just 3.5 seconds and increases maximum velocity to 171 mph (275 km/h), which is still limited from the factory.

Gallery: Mercedes-AMG GLC63 S E Performance (European Model)

The BMW X3 M40i and X3 M rivals have rear-biased all-wheel drive, a nine-speed dual-clutch automatic transmission, an adaptive steel spring suspension, and rear-wheel steering. In the case of the flagship version, the 6.1-kWh battery pack has enough juice for a purely electric range of 7.5 miles (12 kilometres). Stick to the base AMG model and you get five driving modes while the more expensive variant has eight. In addition, the 63 has active roll stabilisation instead of rigid anti-roll bars.

With great power comes great responsibility, which is why the range-topper has 390-mm front and 370-mm rear brake discs instead of the base model's 370-mm front and 360-mm rear setup. AMG fits six-piston calipers at the front of the 63 whereas the 43 only gets four. The two potent SUVs largely share the design, but the 63 gets an Edition 1 with exclusive accents, including 21-inch forged wheels with a matte black finish. The limited-run version also comes with an indoor car cover.

Having already debuted the Benz GLC Coupe, the AMGs can't be far behind, especially since we’ve already seen our fair share of spy shots.