DDR = double data rate.
800x2 = 1600mz, nothing wrong with your ram.
and sandy-bridge should be able to utilize higher frequency ram.
You will not gain any performance increase from OC'ing ram.
You get higher frequency = Good.
You also get higher CAS latency = Bad.
Games rely more on lower CAS latency, should be around 9.
No need to upgrade just yet, stay with sandy-bridge atleast until the next generation.