I bought my 914 4 years ago. I inquired to a couple about 914-6 conversions. They laughed and told me to buy a Boxster. I drove my 914 for 4 years along side my Mazda 3. Then I bought a Boxster. I'm still doing a /6 conversion - but boy that Boxster is fun to drive. I think the Cayman is nicer looking - but they aren't cheap enough when I can get a low mileage mint condition Boxster S for under $20k.
As for the 911 - why do I want a sports car with backseats?
But more seriously - the Boxster/Cayman are capable of more than most can do yet are tons cheaper. Sounds like a good deal to me. I just don't think the 911 is worth it.