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