From a chick's POV:
Carrera, eh. 911 is a much classier car. Depending on what kind of chicks you're going for, you might want to consider the a 356. Mmmmmm.
Cayenne, Boxster are both turn-offs for any girl who knows the first thing about cars.
M3s are pretty, but don't hold a candle to a 911 or 356 IMO. I'd rather date a guy with a Honda than an M3.
If you're going to get a manual, go Porsche. For an automatic, go M3. If you do end up getting a Porsche, look up your local Porsche Club of America (PCA) if you're in the States. Good hook-ups for mechanics and a great social network.
