It has been on my todo list for almost a year but I finally upgraded my driver seat. My old Arizen seats were great on the street and a vast improvement over the stock bucket seats on the autocross or road course. However, the allowed to much body movement, especially since I just have a 3 point OEM style seat belt set up.
So I've now installed a fixed back racing seat, the Sparco Evo II. At 6'3" Its a tight fit with a helmet on but it is about the same amount of headroom as my old setup.