Dude -
Speaking here as "an old fat guy", you don't have to do anything to justify what you drive. Quit worrying that you'll be a cliché and do something for yourself that makes YOU happy. When I'm too old and fat to climb in and out of my Boxsters, I'll get a Cayenne GTS.
No need to keep it secret either. The 20 year old girlfriend? That's what you keep secret. The Boxster you take out and drive. The 20 year old girlfriend you can hide with in the garage.
And just three cars? You're a rookie...
Go find yourself a nice 986 and enjoy your life!
