A boxster or a miata will trounce all of the above named cars in the fun factor. This is said as a present g83 owner, and a former s2000 owner (had that one as a weekend toy)
The m4 vert is an all around amazing car, that's exceptionally fun to drive. I think it's a perfect dd. If I were to go back to 2 cars, though, I'm pretty sure it would be a boxster in the third bay. The z4 is nice, but can't hold a candle to the p car. The m4 is big, and a huge part of the weekend car point for me is zero compromises- no need to account for much beyond driving enjoyment.
Drive a boxster and you'll likely end up buying one
