Definitely get a used car. Anything below 20k and new will probably be boring as hell. I'd go for a cabriolet perhaps. The BMW 3-series in original condition is just the sort of car that works for almost every instance. It's old enough to look different from most of the 90's and 00's cars, but the car isn't so old it's impossible to live with. It's understated compared to the M3 and you won't have to deal with the BMW-driver stigma that you tend to get with a M3 and later 3-series models.
I'm hunting one of those down for myself currently. You have good taste sir. ^^