sandybridge imc will only go up to 2133 (or slightly higher with fsb overclock), so no need for 2400.
I'm running 4x 4gb samsung hch9 at 2150 on a 2500k, with a 100.8mhz fsb
edit: can run these samsungs at c9-10-10-28, 1t, so it's just as fast as 2400-c12
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