get the 1.5v ones. I thought they made the beast ones in 1.5 volts but I guess I am wrong. Just pick the brand and type that you like and get the 1.5 volt ones. The smaller heatsink ones are better for fitting well with CPU coolers.
2x8GB is the best bet, 4x4GB is additional and un-needed stress on the MC (memory controller)...Something like the Ripjaws X or Snipers in 2x8GB 1600/9 would be a good choice