I'm not sure if CNPS9500 would work. It looks like its designed for Socket 775 only. However if you've used it on your previous AM2 machine, then it would definitely work. You shouldn't be worried about replacing it.
But if you're looking at some moderate overclocking on the 9850 BE, then you should consider getting a better heatsink. I would personally recommend Thermalright TRUE-120 Extreme.