According to the nvidia 680i overclocking guide (http://www.nvidia.com/docs/CP/45121/...erclocking.pdf
) the maximum safe voltages are 1.50v for the SPP and it says "any voltages not mentioned are best left on their auto setting, so I wouldn't have even gone that high.
Why do you need to go that high anyway? a single
8800GTX will beat out any DX9 card easily and If I read correctly you have 2 in SLI. I'd say just keep the voltages down so you can extend the life of that monster investment. If you really want to OC it, sorry, I can't help you. I just wanted to put in my 2 cents.