The S will obviously be better, so if money is not an issue then why not, although surely with you being 25, the ongoing insurance costs will be much higher? However, the 2.7 will blow you away anyway, and if you don't drive the S you'll never know what you're missing. I knew when buying mine that if I'd brought an S out I'd probably not be happy with a 2.7, so I didn't test drive the S and saved myself a small fortune. The 2.7 is more of a car than I can handle anyway, all I have to do now is avoid the continuous temptation of testing driving a 3.2.
As for extra's, if you're not planning to keep it for a long time then go easy. The only thing extras will do is make it easier to sell yours from among the hordes of cars that will no doubt be on the market whenever you go to sell. However, you will lose a fortune on most items. The only things I'd recommend are the heated seats for top down driving in colder weather, the wind deflector, the parking sensors (cheaper than replacing the bumper) and I'd highly recommend whatever variation of stability managment is on board these days, it keeps you out of trouble on the main roads and you can always switch it off on the track. If you have a bit of cash, I'd also opt for the partial leather. You won't lose too much on those but if you start going for really expensive things like Sat Nav, BOSE, etc you'll just be throwing your money away, unless you're planning to keep the car for a long time and you want to spec it to completely suit yourself.