Apparently some SB boards don't play nice with 1.65V memory and it looks like going forward Intel is driving for lower and lower RAM voltages.
Overclocking RAM now is by whole multipliers, I think the one above 1866MHz is 2100MHz. A lot of review sites have therefore kind of stopped overclocking the RAM because the adjustments you can make aren't nearly as fine as they use to be. Regardless anything over 1600MHz is overkill; it will cost a hell of a lot more and yield marginally better benchmark performance.
From what I have read the Snipers are good Low Voltage sticks with good timings/speed but have very little overclocking headroom. They are very much a what you see is what you get kind of deal (which is good in some ways, bad in others). I have also noticed a lot of RAM put out for SB to be that way as well.