GTX 650 TDP 64W
GTX 760 TDP 170W
CPU - assume 125W for typical AMD CPU, Intel CPUs are generally lower
Allow 40W for other components
Allowing for most of this to be on the +12V rail and maximum load on this rail to be 80%, you want a supply rated ta 500W or 42A on the +12V rail.
I recommend a good quality 600W supply or higher to be safe.
XFX Pro 650 or XFX Core 650
Antec HCG 620
Seasonic 650W (models G, S12G, X, OEM, any Seasonic model is fine)