Audi A6 has four doors, but it doesn't look like a sedan. Its stylish flair and sweeping lines evoke the sportiness of a coupe. Now in its fourth model year after a smart redesign in 1998, this luxury entry possesses clean lines that are still fresh and forward-looking, with new, fussed-over features and modifications for 2001. The A6 is chock full of amenities to help it compete with such luxury sedans as the Cadillac Catera, Mercedes Benz C280, Lexus GS 300 and Infiniti I30t, all of which start in the $33,000 to $37,000 range. Audi believes the A6 will be popular with buyers who have difficulty justifying the prices of the BMW 5 Series and Mercedes-Benz E-Class. In spite of its fine competition, the A6 is a standout from one end to the other, exuding the confident air of a jewel whose every detail has received a thorough polishing.