Synchronous speed for 1333MHz = 333MHz FSB = DDR2 667 = PC 5300. If you don't plan to OC at all there's no need to buy anything better except for potentially lower timings/command rate. Personally I'd go with DDR2 800 in case you change your mind, as it'd be a shame not to OC any C2D even mildly, much less one of the 45nm parts.
Edit: N/M just saw you were getting an Intel board. Only reason for faster than DDR2 667 would be if you planned to get a 1600MHz FSB CPU in the future, in which case you'd want DDR2 800.