New RAM - let bios Auto set speed or Manually set the speed?

So i installed new ram.. from 8G to 16G, from generic to corsair vengeance, from a DDR3 1333 to DDR3 1600. In my bios, via ASUS UEFI bios utility, I checked the speed, the speed is set to auto, but running at 1373, there is no 1333... should i leave it on auto or manually change it to the faster 1600, which in the bios list there is no 1600, the closest speed 1648.

MOBO: ASUS P8H67-M PRO/CSM - (manufacture says board RAM speed 1333??? but geek squad lol, said i could put in the 1600)
POWER: corsair 500W
CPU: intel i7 3770
GPU: saphirre radeon 6850.

I am guessing I can just manually set it, but seeing i am a total noob about this, I thought i would ask someone who actually knows what they're talking about.

thanks for your time!