I suppose I'll chime in since I am in a similar dillema... My limiting factor is storage space. I don't have the luxury of having an SUV and a "fun car" at this time. So, I need to wrap them both into the same package. Is the X5M a sports car, nope. But it may satisfy that niche while offering the utility of the SUV. I'd love to park a 911 TT in my garage, but that would put one of our other cars in storage or in the street (which is not doable in my area).
My point is that the "get a 50 and an older M3" is not always an option.