You need to keep in mind as well that the Lightning card is a overclocked card. So it wont be your typical GTX770 it will use a little more power. For me personally I would spend a little more on the power supply but that is up to you sir.
Here is the link so you can see the max power of a normal gtx770 230 Wattshttp://www.geforce.com/hardware/desktop-gpus/geforce-gtx-770/specifications
I would say something in the 650 range would be a nice sweet spot.