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#31
I agree with the other posters on whether running DDR3 RAM at higher frequencies makes that much of a difference. It doesn't, and this has been demonstrated by reviewers on several reputable websites. I think you'll get a lot more bang for your overclocking buck by raising your CPU multilplier on that Black Edition chip than focusing on the RAM.
Having said that, I'm running my four 2GB sticks @ 1600MHz with CPU/NB voltage set at 1.22v and RAM voltage at 1.65v. Hard to say whether those setting will let you run two 4GB sticks stably on your board using your chip. You'll have to experiment to find out.