500k?! Then you might want to take a look at a used f430, or if you don't mind spending a bit more, a 458 italia.
If you want a classic Ferrari, then a 355 is the best way to go (best looking Ferrari pininfarina ever designed, my opinion)
A Maserati Quattroporte, used of course, is a lot better than a BMW 7 series, not on luxury but on exclusivity (makes you look more formal and serious, more like a very successful and stylish person) and the noise that it makes... Also, it's better looking, the badge is a lot superior (I mean everybody has a BMW, not the same story with Maseratis) and it was made in a time where Maserati was owned by Ferrari so it's a four door Ferrari, kind of.
Bes of luck dude