It had been a a couple years since I drove the Boxster so I took one for a spin recently.
I was somewhat disappointed. It's very refined and I was expecting more. The steering, like all EPS racks, is "meh" at best.
I've yet to drive the new Z4, but I will say the M2 is way more fun than the Boxster! I think most comparison tests have expressed similar sentiments. Looks like I will be staying within the BMW family with my next purchase.