We've had 2 Audi A6's since 1999. Both relieable. The first was a 1999 C5 A6 saloon (QUIGGS!!) 1.8T. The only problems were back in 2005 when the car had done 110,000miles. The ABS pump broke and the MAF too, both replaced, the first costing £1,000... After this no more problems before we sold it 2months later... These problems probably occured only becuase the car had skipped the past 2 yrs servicing... the current one is a C6 A6 Saloon 2.4-V6 SE, no problems as far apart from the MMI has started rejecting the CD player, TV & DVD-Satelite Navigation...
We also have a 1993 Mazda 323 LXi 1.3 16-valve 3door. It only ever gets used about once every 3months. Starts first time all the time, the only things that have been replaced in its life are tyres, exhausts & batteries.