It's a bit of a surprise that the Audi Coupe GT doesn't have more friends. It has the capaciousness of a sedan with the sleek silhouette of a coupe—and the sports-car performance chops to match.

Audi ensured no significant performance differences between the RS5 coupe and Sportback, which has an almost identical weight to the coupe. Beyond rapid acceleration traction, Audi's Quattro AWD ...