Ah I just lost my post by accidentally posting that. FAIL. Anyway ignore that.
For overclocking you need high speed RAM otherwise your overclock will be limited by your RAM. So you should go for 1600MHz; the lower the CAS the more performance but don't spend too much more for lower latencies. Voltage doesn't matter as long as its under the DDR3 spec (1.65v). Don't limit yourself to 3.4GHz as these processors can go much higher easily =].
Hope I helped.