C3 also allows for the use of 4 sticks of DDR3 @ 1333 due to an improved IMC. Easiest way to tell is the C2 will be GI and C3 will be GM. So while you didn't go wrong with the C2, if you had the $10 to spend then it would've been nicer to have the C3

If you are with in your time frame, you could exchange it for the C3 version.
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On the move to AM3 from 939!!