Think you written off the 4 seats now but would look at an Jaguar XFR over an M3, the RS maybe out of budget, they are fun.
Just sold an SLK, they are nice compared to a 350 inside, quick, but they don't like corners I found, disappointing in my view and they starting to show there age (my view).
Z4M are fun, cayman are nice too, but make you cry a lot if they go wrong 😃