1.7v is my max for passive cooled ram. Saying that, there is no need to run ram at 1.7v if it's max stable speed is achieved at a lower voltage
My older ram LOVED voltage, and it clocked well above it's rated speed and the speed continued to increase right upto 1.7v - on that ram, the ram speed could increase even further with higher dram voltage, but I self limit it to 1.7v for daily use. On the flip side, my current ram HATES voltage, anything above 1.65v causes instability. It reaches it's max stable speed at 1.6v, so I leave it at that.
Moral of above - I test my ram to see what the max stable speed is for the ram without going over a dram voltage of 1.7v, if the max stable speed is achieved at <1.7v, then it is set to run at that lower voltage
EDIT: Disclaimer: It is your choice to OC your dram and run a dram voltage higher then that specified for your ram by your ram manufacturer. You take full responsibility for running your ram beyond the manufacturers specifications. My comments above are of my own experiences - YMMV.Edited by un-nefer - 12/7/12 at 8:24am