Max, don't think I can help you much here, I feel the same way. I love my car, but next time around I'm not sure if I will buy a new Boxster or a used 911. One of my friends has a C4S and the other has a convertible Carrera. I love the lines of the 911, and it sure would be nice to have 300+ hp and rear seats for the little ones.
On the same lines, I love dropping the top after work for the ride home, but if I went the 911 route I would probably buy a coupe. After autocrossing my car this year I finally realize what an amazing machine it is, and I must say that during the Tail of the Dragon trip I would have been scared of driving a 911 the way we were ripping our Boxster's around the curves.
I guess the only way to make the decision is try and get some seat time in a 911 you would consider purchasing, compare it to the Boxster, and go from there...
http://world-class-motorcars.ebizautos.com/detail-1999-porsche-911-carrera_4-2275264.html
Nick