Well one of the other reasons that I haven't OCed my GTX more than I have is because I haven't been monitoring the card temps. I know those cards run hot anyways so I'm not worried about a mild OC to 600/1900.
I my E6600 got into the mid 50's after 15 hours on Orthos at 3.51ghz, and low 60's at 3.6 after several hours. I have yet to see it hit 50 at 3.51 during actual gaming though, and this is playing Medieval 2 and Supreme Commander. The Tuniq cooler is really quite a bit better than the Zalman cooler I originally had.
Looking forward to putting a quad in later this year after the prices drop.