Go on a track day or even better, one of those driving schools, as many people who've been on them say that their increased ability to control and handle a car was a better investment that most modifications.
You see that all the time at the 'ring, for example our little Toyota Corolla VVTI (189bhp Celica Engine, 3 big blokes and all our camping gear!) catching up and harassing a M-Coupe (one driver, 321Bhp) in the dry!
No good for drag races, but they get boring anyway, corners are the new black!
I leant more in 20 mins with Matt Becker driving me around Rockingham in a 911 Turbo than in three years of me owning a daily driver M5!
Ivan.