A few things to keep in mind:
1. Remember the 9600 Pro is STARTING at $199.99 - the 9500 Pro has just recently dropped below $200.
2. This isn't a matter of 9500 Pro vs. 9600 Pro, its a matter of is the 9600 Pro a worthy sucessor to the 9500 Pro.
The 9500 Pro had a short production run and quantities will soon be scarce. Soon, the only card you will be able to get (reliably) will be the 9600 Pro. Were we going to be stuck with an underwhelming replacement to the 9500 Pro? The answer is no. The performance at stock speeds is ALMOST as fast as the 9500 Pro, which is impressive when you consider how awesome the 9500 Pro is. Then you factor in a large, relatively easy OC head-room and this card is worth getting excited about.
Also, in the newest game benchmark, SplinterCell, both the Nvidia and ATI newer generation cards fared much better than the older generation cards. While it remains to be seen if this is or is not a valid trend, its something to keep in mind.
As far as an OC'd 9500 Pro vs. an OC'd 9600 Pro....remember that the 9500 Pro's were only OC'able with the "tweaker" consoles AFTER a vidcard BIOS flash which is not for everyone. And even then, it did not OC a ton.
A 40% increase in clockspeed is nothing to sneeze at. For reference, a 40% increase in a P4 3.06Ghz would be an OC to 4.28Ghz. Not bad for a simple click of the mouse.
P-X