I run my G3 at 240/500 and I could raise it a bit more but I didn't see the point. I'm running at Ti500 settings using Gainwards expertool, which I believe works with other Nvidia based cards too. you could always get the coolbits hack, which enables hidden features in Nvidia drivers that are already part of the drivers. you will gain a tab on your advanced display properties allowing clock adjustments.
AOL-For people who like to pay extra for their SPAM