If I were in your position, I'd buy a Elise or an Exige. But then, the wife and I work together, so I can afford to have one of our two cars be completely impractical.
Like a Boxster, for example.
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1999 Carrera 4 • Aero kit • 4" UD Pulley
My Corvette doesn't leak oil... it sweats horsepower.
If you plan on doing a good deal of track/autocross use then I'd go with an Elise or Exige. If you are looking for a cruiser that can hold a few friends then an M3 convertible. I guess it kinda depends on your budget and what your intentions are, but there are a lot of other options.