A lot of people would be surprised at how upgrading all the squishy bits on their car really makes a noticeable performance difference, as well as increasing the fun factor. Look at upgrading things such as your sway bar (and end links or the stock ones will snap), transmission mounts, engine mounts, control arms, shocks, springs, and anything else that will cause undesired component movement on your driving.
Trust me, it will be a vast improvement and best bang for your buck. Going fast in a straight line is fun until you need to take a turn...