I have an SRT4 right now, and its not about the speed
its about the handling and not just straight line speed. and i dont have my mind made up, it was kind of made up till all you guys slapped me down
Do you have the skill to use the handling? Have you been to the track, taken an SCCA or Cascade Sports car club driving school to know? If not - may I suggest taking your SRT4 to one - and seeing how far you are from using what this car can do?
On June 4 Cascade is having a driver training and HPDE class -
http://www.cascadesportscarclub.org/ - do it.
Honestly, you have to be very, very good to really take advantage of that Porsche as anything more than penile extension - unless you are Fernando Alonso's long lost cousin - the handling thing is just an excuse. Heck, if you want handling, you do not but a Porsche, you buy a Lotus...
At the end of the day - for most of us, mere mortals, sports cars are about the experience, not about the handling and being able to use it properly to it's full extent. Heck, I had a Lotus and won several regional autocross class events with it, I won some dirt rallycross class events with my old BMW - and I have no illusions about actually being able to truly scratch what it (or the Porsche, of even my first race car - a Miata) can do as far as handling is concerned...
While I never drove a Cayman, I got to try a Boxster and it is a fun, fun car, but as far as an "experience" and sense of occasion while driving it - a used 911 for $15K is more of an experience and occasion imho...
Heck, the only reasonable way to not lose your shirt on sports cars is to go the opposite way - get into older, classic sports cars that will never depreciate - sure, there is maintenance that will cost a bit more, and when it comes down to it - your SRT4 will be faster around a race track by a capable driver than an old car - but it will not be anywhere near as much fun to actually drive it around that track fast, it will not make the same glorious noise, it will not attract all the attention that a nice old car will - and it will not give you the same kind of satisfaction when you actually get it around a race track fast.
In other words - buy a 70s Alfa Romeo or a 80s Porsche... that's a proper way to enjoy unique cars without losing tons of money.