Increasing mobo voltages

I have recently aquired an epox 8rda3+ which clocks ok, 220fsb no problems, but was after a bit more. In the past I have kept away from increasing motherboard voltages, and was wondering how safe it is to increase power a little. Currently I'm @ default c/set voltage of 1.6v, how dangerous is it increasing it to say 1.8v? I have a slightly larger than average nb hs with temps quite stable atm, cpu 40C and other board sensors (I don't know which these are respectiveley) 25 and 27C - full load that is ;)

thx.