Yeah, seremify sums it up well.
You can't go wrong with either the C class or 3 Series, or the IS250, however these are at the upper reaches of your budget. That's the way to go if you're focusing on prestige and luxury.
Then again, you can get a bit more kick from lower priced competitors, such as the Subaru Liberty, or even the new Nissan Maxima (I think it won the Large Car of the Year award or something), as well as the Honda Accord Euro/Regular.
The 3 series and IS250 are somewhat outdated and a new model is expected soon. The Liberty and Maxima practically came out this year while the Accord isn't that old either.
Reliability conjures up the word 'Toyota', but you're probably looking at an Aurion. You will lose out on prestige and luxury, but you'll have 200kw and an unbreakable engine.
I personally wouldn't go for this either. V6 Camry for over $40k? Right.
Another consideration is that the base model BMW/Merc/Lexus won't have all the top notch features. The Maxima/Accord/Liberty/Aurion will all have sat-nav and leather and stuff considering the most expensive models are in the same price bracket as the base German/Lexus models.