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Which of these seems the best: Kingston Hyper-X, Corsair XMS3, or Crucial Ballistix. All 1600mHz. 4x4 setup. I am leaning towards the Corsair XMS3.
It doesn't really matter, they're all good. Memory makes next to no difference other than how much when it comes to choices between good brands these days. Back when overclocking memory gave gains it was different, now it makes none.
Aside from technical specifications, which you have already covered, picking memory comes down to two things:
Warranty and return policy (RAM is the highest DOA item, make sure you can return it if it goes bad)
Aesthetics - how well it looks. Some people like to color match their interiors or just like the looks of one heatsink over another.
Aside from that, it's all basically the same, and it's all made in one of about 3 places world wide.