New model launches and re-launches by Audi never fail to grab massive amounts of publicity. But given that the Audi A6 goes head-to-head against some the biggest heavyweights in the executive saloon category - think the BMW 5 Series, Jaguar XE and Mercedes-Benz E-Class - the current A6 model sneaked out with barely more than a whisper when it came out in 2011.