Audi's A4 and A6 exemplify the automaker's best qualities: sophisticated design, excellent craftsmanship, and superb road manners. But the company has some catching up to do if it wants to win more American customers.

A pair of Audis showed up on my test drive schedule as winter morphed into spring in the Northeast. They weren't the newest models in the line -- the 2011 A6 is being replaced by the redesigned 2012 model as this is written, and the all-new A7 arrives this month. But they reminded me why I like Audis so much -- and helped me to gauge how close Audi has come to reaching top tier status in the U.S.

2011 Audi A4

Audi is the late arrival to the American market compared with Mercedes-Benz and BMW, and has been trying hard to catch up. So far this year, import luxury car sales have trailed the overall market, but Audi has been outperforming its German rivals, as well as Lexus. It takes more than velocity to compete in this arena, as we shall see.

Revamped a year ago, the compact A4 remains the core of the Audi lineup. Along with its sportier sibling, the S4, it accounts for nearly half of Audi's car sales. Audi has had less success establishing the larger A6 as a second core model; Audi sells only a quarter as many of this model as it sells A4s. That contrasts with Mercedes, where sales of its E-class nearly equal those of the smaller C-class, and BMW, where sales of the 5-series run at about half the rate of the 3-series. More