Car and Driver has gotten its hands on the 2013 Audi S6, BMW M5 and Mercedes-Benz E63 AMG to see which powerful luxury sports sedan reigns supreme. Will it be Audi's S6 with its new twin-turbo V8 and Quattro All Wheel Drive, BMW with its very own twin-turbo M5, or Mercedes-Benz with sledgehammering E63 AMG?
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