I don't have a lot of wheel time in the Cayman, but I think it might be the right car for you if you can live with two seats and limited storage. The Cayman R I drove at the Porsche World Roadshow was a blast and responded well to my commands. In my mind it would be a great weekend car, but I'm sure I would be happy to DD one if I didn't have kids.
If you need a little more space then a clean 997 Carrera S would be a nice choice. I had an '09 C2S so I have a little more experience with this car. The steering feel and brake feel are fantastic. Add in the compact size and great visibility and the 997 is a fun car to burn up back roads with. The rear weight bias takes some getting used to, but once you get a feel for it you appreciate the added traction coming out of corners and the balanced feel under braking. My only real complaints with the 997 are the low seating position, stiff clutch and the price.
If you are interested in defying physics then the GT-R would be a good choice. Again, I owned both a 2011 and 2012 GT-R so I have first hand experience. The GT-R builds speed so quickly and holds the road so well that you feel a bit invincible when behind the wheel. The steering is very fast and has more feel than the M3. The brakes also do an admirable job hauling the heavy GT-R down and have good feel. One thing that you might not like is that you have to push the GT-R harder than any of the other cars you are considering to get a good rush. It can be a bit boring at speeds that would have your palms sweating in other cars. The ride is stiff and the tires are noisy which will get old on long commutes. Finally, the GT-R is big and can be hard to place in a corner until you get used to it.
If you want a fun car that can also be an easy to live with commuter then the E9x M3 is a fantastic choice. Yes, I owned one of these as well. The M is a great size, has good visibility and is plenty fast. Also, you can get a slew of comfort and convenience options that make the car easier to live with on a daily basis. The brakes and steering offer admirable feel and the chassis gives you a lot of feedback. The M3 is not a car that will bite you without warning assuming you are showing the it some respect. About the only real complaint I had about the M3 is the lack of low-end grunt. Besides that the M felt every bit as fast as my 997.2 C2S.
I highly recommend you get out and drive every car that is even remotely on your radar. It might take you a bit longer to get your new ride, but at least you will know how each car fits you. Plus, it is a lot of fun.