Do I upgrade my pc or wait?

i have an 8600gts 256mb and 2 gb ram 3.00ghz processor xp 32 bit 19 inch lcd 1400*900 resolution 2 tb hard disk i got enough money to upgrade to a 9600 gt is it Worth it i run these games lag free call of duty modern warfare 1 and 2 ,call of duty world at war, far cry 2 ,crysis ,prototype ,spider man web of shadows ,burnout paradise, fallout3, mercenaries 2 ,fear 1 ,battle stations pacific and gta4 ps i want to make my pc faster and i also gave a ps3