The AMD equivalent of the GTX 680 is the 7970, if you prefer it, Haxorico. I tend to go AMD for video cards, if only because of their nearly equivalent prices / performance compared to nVidia's stuff...while having a smaller market share. It's my civic duty, so to speak.
The 7970 is a little bit cheaper at the moment, however, compared to the GTX 680 ($20-40)...how that will translate to where you are, (or whether even either of these cards are available to you), I'm not entirely sure.
(edit) For power supplies, like Kryptonyte, I'd probably recommend something about 600-700. Make sure it's a decent brand, though.