This is an interesting review of the Cayman on Car & driver.com.
Many of you may have seen it, but if you didn't check this out.
Quote:
Porsche Cayman S
The Cayman S is the new hard-hat version of the Boxster. Its fixed roof and an extra crossbeam behind the seats make it twice as stiff as the Boxster S and 10 pounds lighter, Porsche says. The Cayman also has a different front bumper, titanium-colored body accents, and extra body curves—its hips rise a half-inch higher than a Boxster’s to meet the swoopy slope of the roofline. And it has a small ducktail spoiler that deploys upward on struts at 75 mph. Its only engine is a 3387cc flat six that dynos at 291 horsepower and 251 lb-ft of torque, 15 more of each than a Boxster S. This promises nominally better performance, which, insists Porsche, justifies a base price of $59,695—that’s $10,400 less than the cheapest 911 but $5800 more than a Boxster S. There’s not much reason to pick the Cayman over the Boxster unless you love its shape or need a bit more cargo space. |

Granted it's faster but I think I would just do fine with the boxster S.