I also, drive a Mercedes C Class 350 CDI Sport 7 Speed Auto. It's good but a bit boring and I hate the foot operated hand brake.
BMW 3 Series 3.0D or 3.5D much better to drive but pig ugly externally and nasty on the inside.
If you are going the saloon route, then the new BMW 5 Series is the one. Fabulous interior and the highest NCAP rating. Looks good too, but too long for me as is also the C Class. So I prefer Golf GTi which I feel is a good compromise for
moi!
New E-Class saloon is a mess in styling. The old one looks much better. However, too many of these around as mini-cabs.
Coupe - E Class is really very tasty. BMW Coupe too tame and boring in the looks department
Audis - A3, A4, A5, A6 all quite horrid to drive. Niceish interiors and they can be specced with 4WD.
Stick with the Golf GTi, or buy a 5 Series.