On the Audi S6 and the Audi S7, the important numbers are 420 hp, 0 to 60 in 4.9 seconds and a combined fuel economy of 20 mpg.

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Pointed toward his 18-acre compound in Marin County, California, Sean Parker rips through the night fog on the Golden Gate Bridge in a stealthy Audi S6 that masks a Lamborghini engine, one pale hand on the wheel, the other toggling through thousands of songs uploaded on the car's sound system.

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