Googel and That link will gave you.

Watch how far you overclock just because you can reach a extreme  overclock don't always mean better performance, even if your temps are in the safe zone........example this processor at 4Ghz is the sweet spot. Between 4Ghz and 4.5 at least on water-cooling there is not so much of a gain as there is between 3.5 and 4Ghz in real world apps just extra heat and wear.

This holds true with your GPU Watch your benchmarks and you decide wheather going so far is worth the strain and ware on the components or backing back a bit is better to run in real world apps just not benchmarks.

http://www.mersenne.org/freesoft/  System stability test.
http://www.ozone3d.net/benchmarks/fur/ For GPU Stability test
Passmark for over all test.
Heaven and 3dmark for GPU benchmarks...Also known for bragging rights...LOL