With 617 horsepower and a 208mph top speed, topping the Mercedes SLR McLaren was no mean feat. Mercedes nearly managed to pull it off with the new SLS AMG. The gull-winged supercar was unveiled at the recent international auto show in Frankfurt to rave reviews. But it still falls a shade short of its predecessor's bragging rights, so the German automaker is reportedly working on an even more exclusive, more powerful and more capable SLS AMG Black Series.

Following in the Black Series that has given us the SLK55, CLK63 and SL65, the SLS Black is expected to gain some extra power and lose some weight to optimize that vital power to weight ratio. Sources expect the 563hp and 479lb-ft of torque from the existing 6.2-liter V8 to get a boost past the 600hp/500lb-ft mark, coupled with a 50kg weight-shaving scheme to drop the "stock" SLS' 0-62 mph time down from 3.8 seconds – already faster than 99% of the cars out on the road – to below 3.5 seconds, and the top speed up from 195 mph to 208.

Of course the added exclusivity won't come cheap: insiders expect the price to jump by half to over $250,000 when the SLS AMG Black Series hits the market in 2013.

Mercedes-Benz and McLaren have a long-standing relationship. The two outfits have won Formula One championships together, and collaborated on the Mercedes SLR McLaren. But while the two continue their collaboration in F1, their road-car programs have gone separate ways. McLaren recently unveiled the new MP4-12C supercar online, and what you see above is Mercedes' answer.

Like arch-rival BMW's now-defunct Z8, the SLS AMG takes its retro cues from the company's history – in this case the iconic Gullwing 300 SL. The SLS has been developed entirely in-house by the German automaker's AMG performance division, and packs the company's ubiquitous 6.3-liter 563hp V8 engine mated to a dual-clutch transmission. Unveiled at the Frankfurt auto show for the first time, the SLS AMG sits atop the Mercedes range with a quarter-million-dollar price tag.

There's been a horsepower war being waged between German automakers for years, and Mercedes has been one of the biggest armies on the front line. An endless succession of big V8 and twin-turbo V12 engines have seen to Benz's dominance, housed in everything from station wagons to sportscars. Following the likes of the SLR McLaren and SL65 Black Series, the latest of the latter is almost here. But while the SLS "gullwing" will shout the battle cry of the horsepower wars with typical zeal, confirmed reports now indicate that it will also offer a more peaceful solution in the form of an all-electric version.

While the conventional SLS will be powered by a 6.3-liter V8 producing 563 horsepower and 479 lb-ft of torque, the electric version will produce the equivalent of 526hp and 649 lb-ft, offering potential buyers no excuse for sticking to the fossil-fuel-burning version once the electric model makes its debut. The electric Mercedes supercar promises to accelerate to sixty in four seconds flat, that motivation being delivered courtesy of four individual electric motors and a 48 kWh lithium ion battery pack. Given Mercedes parent company Daimler's recent investment of $50 million in Tesla, it's safe to say that the California startup will be helping out in the development, but while a launch date for the electric SLS hasn't been revealed, sources expect to see it on the road by 2015.