unknownofprob is correct upgrade your PSU , will not cut it for that card
for a quality PSU get a seasonic/(xfx - also made by seasonic)/ any PSU from the corsair HX,TX or ax range of psu's
Watch dogs shows that r9 270x is just 1 fps behind gtx 760 and I am gonna get 270x cause amd have made new drivers to compete with 760 performance thanks to all