I know we don't have the same cards, but I use the stock cooling on my card. I keep the fan at 50% using EVGA Precision because RivaTuner has many options I don't use right now. I tried all sorts of speeds above 50%, but with the sound of my case fans and the space heater during winter, I cannot hear my fan at 50%. I can just barely hear it at 55%. At 60%, it becomes slightly easier, but I still have to listen for it. But once I get to 65% and above, it's audible. It's not "too loud", but I just want as quiet of a system as I can have.
For example, I set the NB fan to 50%. It used to run at 100%. It has been weeks since I have done this, and there have been no problems with the reduced fan speed. All I get is pure silence. I love it.
What I'm saying is that try EVGA Precision or RivaTuner. The fan speed is probably at 35% right now. If you want it to be quiet, but still much faster, then gradually increase it until you want to decrease it due to the noise. Then make sure you set the software up (RivaTuner/Precision) so that it starts with windows, and also so that the setting is applied at Windows Startup.
I'll be honest: my stock cooling is more than enough cooling for my GPU. I have not seen any need for an aftermarket cooler whatsoever. And it doesn't look like I ever will. I'm just saying that it's possible you may find the same to be true for you.
Edit: I know I was talking about 5% intervals, but I used 5% intervals just because that's how I am. You can set it to anything you want.
Edited by TwoCables - 12/24/08 at 11:43am