Audi wanted to bitch slap the M5 and it looks like they're raising their hands. But BMM (//M) is laughing cos it takes a bi turbo V8 to do so whereas M5 is N/A 
RS6 -> 4.2L pumping out 450 bhp (56 more than M5) and 560Nm (60 more than M5). Most interestingly is that it's maximum torgue occurs at very low rpm and ranging from 1950-5600 rpm....Should be able to beat the M5 but no....9000RPM said:
Audi has torque to burn though.