The posher and more upmarket replacement of the old AMG CLS 63, the GT 63 S, has proved to be a proper four-door supercar. However, with a little help from certain tuners, like Posaidon in this case, it can truly mix it with hypercars.

In exchange for just a little under €24,000 ($26,569), the German company can upgrade the 4.0-liter, twin-turbo V8 to staggering numbers: 830 PS (818 hp / 610 kW), hence the RS 830 moniker, and 1,100 Nm (811 lb-ft) of torque – or 191 PS (188 hp / 140 kW) and 200 Nm (148 lb-ft) more than the stock model.

Also Watch: Mercedes-AMG GT 63 S Vs. Lamborghini Aventador S: Can The Super Sedan Beat The Supercar?

Thanks to the extra oomph, the GT 63 S needs a mere 2.9 seconds from 0 to 100 km/h (0-62 mph). Top speed has also increased to over 350 km/h (217 mph). In comparison, the stock model is 0.5 seconds to 62 mph and tops out at 315 km/h (195 mph).

In order to achieve these numbers, Posaidon has upgraded the turbochargers, added an extension to the charge air-cooling system, sports air filters and downpipes with sports catalytic converters. Furthermore, they have also remapped the engine and transmission software, and for improving the driving dynamics, they have used an electronic module to lower the ground clearance.

Normally, we would not have saved the best for last, but there’s a good explanation for that: we’ve already covered it before. It concerns Posaidon’s RS 830+ kit, which lifts output to 880 PS (868 hp / 647 kW) and 1,200 Nm (885 lb-ft) Both the RS 830 and RS 830+ are available for other modern AMGs that use the same 4.0-liter V8, like for instance the GT R.