I bought a couple weeks ago a Vengeance LPX 2666mhz C-16 16 GB RAM package. I know, I know. I probably should have bought a G.Skill or any other more affordable option, but I just wasn't thinking right. But now that I do have this 2666mhz C-16 RAM, should I leave it to the default low mhz or use XMP / manual OC to set the ram at 2666mhz and beyond? For the future, is there much reason to get ram above 2133mhz? On a side not, what is the difference between C-15 and C-16 noticeable or not? That is also something I was dumb to get. A 2133 or 2400mhz RAM with C-15 would probably been the much better deal.