The A6 is Audi's equivalent of the BMW 5-Series or Mercedes E-Class. Unlike its competitors, it's only available with either front or Quattro four-wheel drive - depending on which engine you go for. It's been in production since 1994, and is now in its fourth complete generation, of which the latest was released in 2011. It's refined and luxurious, with one of the best interiors in the business. On the road, although it isn't as good a drive as a Jaguar XF, the A6 is still a solid steer. Older models have always been well received, and should prove a reliable second-hand buy.