It would be an amazing sleeper. I also recommend figuring what you could get for your current car, high-teens I would think, add 20K to it and you would end up with the high 30's. Would you be happier with a later generation Boxster S, or the sleeper?
The sleeper would no doubt be unique and faster, but the resale, should you choose to sell, it would not be very high. Personally, if I could afford it, I would love a 3.6L in my older Boxster, but with my limited budget and a son going off to college next year, I would go for a 2005 Boxster S. Boy I wish I had your choice, have fun,
Ed