I think you've analyzed the issues pretty well but additionally I would want to know the in-service date so you know how long the warranty will last. It's also not clear from your post whether you'd prefer a Z4M or the M3 which would go to your willingness to compromise and/or drive a hard bargain and be willing to walk away. FWIW I'd be wary of the way that car may have been treated and think the price is def high though tough to say how much without knowing all options on the car or is it only the two you listed? Keep us posted though
