if you go with 6300 or 6400 get the p5b or ds3.
the 680i mobo doesn't seem to like the high fsb required for large overclocks with the low end c2ds (they have low multipliers).
680i and e6600 will rip. but that's kinda expensive.
the boards with the p965 chipset appear to be the best overclocker for the (lower) c2ds. 775 actually refers to the cpu socket type. the mobo you have picked out will be fine if you go with 63/6400. it would be okay for a 6600 as well.
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