Hmmm... Mazda6... you actually have to try one if you're considering a secondhand BMW, as the Mazda is the closest you can get to the BMW driving "feel" in a front-wheel drive car.

It's understated, classy and good looking... the interior is well-designed and very austere (unlike the over-exuberant and techno Mazda3) and with very few on the road, you won't see yourself coming and going. Only real problem with the car is the lack of a manual shifter... which takes quite a bit of "oomph" away from the engine.

If you're looking for Benz luxury, while they may not quite have the upscale feel, the Camry and Accord are both very plush high speed cruisers, with great sound insulation (perfect quiet at 140+) and lots of goodies. I'd say Cefiro, as that has a terrific engine (super smooth and quiet), but then that says "lolo-car" even more than an old Benz.

But if your heart is set on a German, I'd get a BMW, at your age.