1,25V is safe to the vrams 
i dont think so, atleast my one cant handel it, above 1,2V i get blackscreen with 100% fan after a while, as higher the voltage is, as earlier the card fails.
I only testet it at one card, the other never failed, but i havent pushed them any further then 960mhz and 1,18V.
I will stay at this clocks, the difference is too less to risk a dead card.
and btw, my 7 year old psu was designed to deliver about 465W, at the wall my pc needs about 540W
So i think i shouldn overvolt them to 1,25V hehe
i dont think so, atleast my one cant handel it, above 1,2V i get blackscreen with 100% fan after a while, as higher the voltage is, as earlier the card fails.
I only testet it at one card, the other never failed, but i havent pushed them any further then 960mhz and 1,18V.
I will stay at this clocks, the difference is too less to risk a dead card.
and btw, my 7 year old psu was designed to deliver about 465W, at the wall my pc needs about 540W
So i think i shouldn overvolt them to 1,25V hehe
1.25V is lower than what could immediately kill the VRMs (Voltage Regulators, not vRAM), but they would likely die from heat long before you discover what's the max you can go with.