Power will come from a twin turbo 4.0 liter direct injected V8 which seems confirmed and apparently also confirms this powerplant for the next generation C63 AMG and possibly will make for a SLK63 AMG as well. Two V8 models will be available one targeting the Porsche 991 Carrera S with 485 horsepower and the other model known as the SLC S going against the 991 Turbo packing 585 horsepower.
Pricing for the base V8 (which will be tuneable and may be the bargain in the range) is expected in the $120k range. The SLC S would be upwards of $180k overlapping with the SLS quite a bit.
With 585 horses and a curb weight projected to be in the 3400 pound range this thing will be a rocket and will surpass the Mercedes-Benz SLS. That seems somewhat odd as it creates overlap and with the SLC being significantly cheaper somewhat undermines the SLS. But hey, those gullwing doors are worth something right?
An entry level V6 should also make it in but that will come after the V8 models obviously to increase volume and profit and margin from development. Good for you Mercedes, this is shaping up to be an awesome car.