[Perfectlap]

well 21 isn't that young (well nowadays). So Having a Porsche isn't too outlandish.

one thing, driving sportscars brought me to the world of Autocross/Driving schools which has made me about 1000X's the driver the average motorist today is.
actually,m After the first event I was a 3X's better driver then I was the day before.
I've avoided accidents that I highly doubt I would have avoided if I didn't have experience REALLY laying into the brake and a very sharp turn of the wheel.

i doubt you'll ever learn to do that with a big sedan. Does Lexus make a good second hand coupe?

So from a safety standpoint, your reaction time and sense of becoming alert to dangerous conditions become far more acute as a sports car driver
IF you make it your local Autocross. In the DC area they do them at the FEDEX Stadium. A huge course where Nationals are often run.

Other good used sports cars
Subaru STI
Mazda Miata
Honda S2000
Acura RSX
Dodge NEON RT(?)

Maybe wait a couple of years for the Boxster. Your insuracne will be cheaper and a low mileage 2000-2004 BoxsterS will be a sports car bargain. Honestly I think its a good car to move up to but not really one to start off with. Learning to drive correctly can be hard on your machinery and Porsche parts out of warranty can be pricey, much more so then any of the cars listed above

p.s.
a BMW 3 series coupe is an excellent safe and reliable car that's not too bad in performance terms.