You'd be mad to sell it for a Z4 IMHO.
My mate had an R reg one which he had bought new when he got his first job. He ran a beat up old A4 as a daily driver but decided to get rid of both and buy an all in one fun/family car when his daughter was born 3 years ago. He has never stopped regretting it since, in fact, i'm sure he cries himself to sleep about it some nights. To put a cherry on the cake. The car was bought buy a mechanic friend who did a type R engine conversion.
My mate had an R reg one which he had bought new when he got his first job. He ran a beat up old A4 as a daily driver but decided to get rid of both and buy an all in one fun/family car when his daughter was born 3 years ago. He has never stopped regretting it since, in fact, i'm sure he cries himself to sleep about it some nights. To put a cherry on the cake. The car was bought buy a mechanic friend who did a type R engine conversion.