For your situation, I'd say get the pond pump and wait for what Q1-Q2 next year brings, but if you are unsatisfied with the way games are playing, then NOW is the time to pick up a new card.
a 5770 or GTX260 will flog your 9600GT pretty well, but a 9600GT is not a complete slouch IMO. A tough choice indeed.
“my goal is speed, full ultra, and extreme gaming” -Ephraim
“Yeah you can always overclock the 2gb memory to 4gb” -jaredpace