Well as the launch of the r9 300 series approach I'm looking at adding a second 290 to my system. Only thing is my PSU is a 750 Watt PSU and I'm not sure if that is enough. Well I know it's just enough from looking at PSU calculators. They say it will need about around 700 watts. But my question. Is it safe to run a PSU at close to max power for extended amounts of time? If not what size psu should I look into? Also my PSU is a corsair HX750 psu