I'm not quite sure whats up with Corsair but you are not the first person I've tried to help on this forum with facing problems with the stick running on 1333Mhz by default
Anyways, I'm not sure what the option is on an Intel Gigabyte board but on my AMD Gigabyte board, enter your system BIOS and go in Motherboard Intelligent Tweaker, select Memory Clock to MANUAL and then raise the memory clock to x6.66. It should now be running @ 1600Mhz
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As for saving electricity bill, what I did with my super-heavy X6 is that I went in the BIOS and lowered my Processor Clock Ratio to the lowest available (5x). My processor now runs at 270*5 = 1350Mhz.
When I need full power for any work/game (which is quite rare as even a 1.3Ghz Hex-Core can run most content smoothly- Team Fortress 2, Opera, Basic Photoshop, Internet Radio), I load up Gigabyte EasyTune6 (which comes with the softwares disc from my motherboard) and raise the multiplier back up to 14x (270*14=3780Mhz). When I'm done with any work/game, I lower it back down to 5x via the same software or just restart my PC.