C63 AMG has now been tested by Sportauto on Nordschleife. Tested with raised topspeed, 030-Package and Corsa tires (R-tires).
It will be official early next year but lets try to predict the result now

For preference, R8 did it in 8.04 min, RS4 in 8.09 min and M3 V8 in 8.05 min (all three also with R-tires).