VW/Audi's are strange...you either get a good one, or you don't. At work we have a few repeat Beetle owners...one of them is there about every 6 weeks or so. It's usually the little things, but they nickle and dime you to death...Taking it a good import shop will save you some money over a dealer, but they can be expensive--or, you have no problems and buy another one.
The Bonneville isn't a bad car...but it's FWD, makes it difficult (and expensive) to work on.
The Caddy's are what I would get if those were my choices, the DeVille spcifically. It doesn't feel as nice as a BMW or Benz, but it's isn't bad. It feels like a dressed up Chevy (and it is), like the luxury is added on, not built in.
You should consider a BMW 3 or 5 series. Good cars. Take care of them, and they will take care of you.