There's a few vids of 600hp RS4s...
One doing 202mph with 3 people in the car

Do they all run RS6 turbos?
I know they all need big fuel pump and injectors, FMIC, downpipe and cats...but are they all on standard 'internals'?
550hp seems the max for standard 'internals' S4, is 650hp a reasonable prospect for standard 'internals' RS4?