Might be news to you, but E63 doesn't have a NA engine any more. It has a 5.5l bi turbo V8 that only revs to 6000 rpm. For that matter, the new M5 engine actually revs as much as the old AMG 6.3l NA engine. In fact, I think with the exception of M838T in McLaren MP4 12C, the new M5 engine is probably the highest revving turbo engine.
Not sure about the highest revving since most of the turbo cars these days redline at 6800 - 7000 rpm much like the M5. It is pretty standard for nearly all the turbo cars.
But, if truly the 6.2 Liter V8 is not being used in the E63 then my comparison must be disregarded.