The Boxster/Cayman sounds like a more logical way to go to me. Taking my Boxster S and my dads Boxster up the coast highway to SF were a couple of the best drives I have ever been on, even though I have done it in faster more powerful cars.
Sorry about the GT3 thing, I haven't done too many AX's recently, just time trials I have never been beaten by any GT3 in my 944 turbo or the 996 at a timetrial. Not trying to bad mouth the GT3, they are a better built car, but not really much faster in my opinion. Slightly yes, but the cost of entry and repair is a lot higher for a slight performance improvement. If cost isn't very important, or you plan on doing endurance racing, get the GT3, otherwise I think better tires and more seat time will make you faster in a non-GT3 Porsche and save money.