I don't think I could keep track of 10 cars, unless I got to hire a team of mechanics to baby them for me. But then that wouldn't really be the same at all... So I'll go with 5. This list presumes I'm made of infinite money of course:
1) An original Ford GT-40, restored to Le-Mans ***-kicking form as accurately as possible. It would be a garage queen, and very rarely and carefully tracked.
2) A Porsche 997 GT2 to use for track events and mod the hell out of
3) A brand new Ferrari 430 Scuderia as my daily driver, unmodded.
4) A BMW 740Li for those occasions where passengers and/or excessive luggage are required.
5) A big-*** used truck, because none of my other cars on this list would be any good for hauling large heavy dirty things around, like car parts and other random projects