Same dilemma; I actually have both sets of RAM in my possession. Which one should I go with? The 2x4GB DDR-1333 RipJaws or the 2x2GB 1600? Both GSkill obviously. Win 7 Pro 64 Bit, AMD Phenom II 965 CPU 3.40Ghz, MSI 790GX-G65 AM3 AMD 790GX HDMI ATX AMD Motherboard, Intel® X25-M Mainstream SATA Solid-State Drive - 160GB.