EVGA 650 GS is an outstanding choice, made by Seasonic. If the rest of your system has average components it should be fine. If you have AMD FX-9xxx series CPU you'll need more power.
My Raidmax PSU here i bought in 2007. I put my GTX 970 in today powered up and it ran great until i tried to play a game then Instant PC reset. This happened to every game i tried that demanded GPU power. Normal web surfing was fine esc.. I did some research and everyone with this issue said people needed a better PSU.
I have an intel i5 3350P chip. My old card was a HD7850 and it was fine, installed new card and like i said instant reset on anything GPU demanding.
So what's the problem? You've already selected a great PSU. 650 watts is enough to power a 980 Ti in the future. If you select 850 watts, you'd have enough to install two 980 Ti's in SLI.