The <$50K performance car market is not crowded by any means, but there are some great choices. The 09 WRX, STi, Evo, S2000, 370Z, Camaro SS, Mustang GT and Challenger SRT8 all have their strengths and offer something for the enthusiast. Like the tire deforming V8 torque? It's in there. Like a high-revving screamer? It's in there. Fashion yourself a rally driver with AWD and blistering turbo power? It's in there.
While the Cayman is more exclusive than the Boxster, I'm not sure it's worth the large premium that Porsche asks for it. Of course, that statement is purely subjective. But, the Boxster showed us that Porsche still has "924" tucked away in their marketing plans somewhere. Now, I don't think the Boxster is the newer 924, but there are some strong similarities. The 924 was expensive in the segment, but had poor resale. Boxster? Same. The 924 had dubious build quality and lacked the substance of the 911, and even the later 944. Boxster? Much the same.
As there are tons of used Boxsters for sale, it tells me that few Porschephiles bought them. Probably lots of leases by badge-seekers that would not tolerate the costs of operating an out-of-warranty Porsche. While none of the newer models are very DIY friendly, the Boxster is especially poor.
If I were spending Wing's money and had the choice between a 370Z and Cayman, I'd get the Porsche. Were it my own bucks, the 370Z is the clear winner.