There is no need to overclock DDR3. All current Intel and AMD processors have an integrated memory controller ( IMC ) that just does not need high speed RAM. DDR3 1600 is the sweet spot for both brands. When I say the sweet spot I mean based on price as much as anything. The gain from DDR3 1333 to DDR3 1600 is a few percent at most. Nothing you will ever notice outside of a benchmarking program.
The only exception is with the new APUs. The integrated graphics on an APU likes the highest speed RAM you can give it.