How much room do I have to overclock ? 7970 and cx500

Spicy_benie

Honorable
May 19, 2012
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My computer is
I5 3570k (not overclocked)
Asrock z77 pro3
Cosair cx500
Sapphire 7970
8gb ram
Vortex 3620
500gb

I've read around and 500w seems like enough for max of maybe 6 months. Im just wondering how much wiggle room I have to overclock the gpu mildly? Can I up the clocks to match the 770 to make me feel better about my decision or do i have to wait to get a better power supply?

Thanks for all the help