I think a good opportunity would be to add faster memory chips or even G5X for the 580. Would get pretty big performance increases, or more so from that since it's likely the core clocks won't get much higher
All that is gold does not glitter,
Not all those who wander are lost;
The old that is strong does not wither,
Deep roots are not reached by the frost.
From the ashes a fire shall be woken,
A light from the shadows shall spring;
Renewed shall be the blade that was broken,
The crownless again shall be king.
- J. R. R. Tolkien