G35 Coupe! Infiniti is another good premium brand. Or since you don't need 4 seats, you could even go with a 350Z.
Heh, I'm almost in the same state of mind, though my budget is a little bit higher. I hate having the same car as everyone else, so that's entering into my decision quite a bit.
Problem with a 3 series BMW is EVERYONE and their dog seems to have a 3 series BMW. There's so many of them I don't think anyone notices them anymore.
Same thing with a Boxter, it's the Porche that everyone can afford.
For that price range it'll be a stretch to get anything decent from MB or Lexus too. The IS250 is a nice looking car though, but I'm not sure what year they released the new design.
You could go in a different direction such as a RX-8, or even a Miata with some nice add-on stuff. Or a Honda S-2000. Or a Mini Cooper S
Back to BMW, you might be able to find a Z4 roadster for that low. Or the Pontiac Solstice, or even the Saturn Sky (that one is pretty rare).
The WRX STi will get you wow factor, but only for it's performance (ugly car IMO).
A bit bigger, you could look at a Jaguar S-Type, nice looking car IMO. Or even a Volvo R60, though not sure if you could find one that cheap. Caddy STS as well. Audi A4.
Sorry, lots of options, not sure I've been a help or just made things worse.