I have a GA-EX58-UD5 motherboard with 6 memory slots. (i7-920 OC to 3.8)Currently installed are CORSAIR XMS3 12GB (6 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model HX3X12G1600C9 G. My motherboard can handle faster memory, so to try and give me a boost, I bought (2) G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 2133 (PC3 17000) Desktop Memory Model F3-17000CL11D-8GBXL. I've read so many different views on this and just need a definitive answer and this forum has always provided me with a wealth of knowledge, so thanks... With what I am working with, what is my best option? Should I stick with the 6x2GB modules at 1600 MHz or switch to the 4x4GB modules at 2133MHz? OR if you have other options, I'm more than willing to listen. I know I should have posted here before purchasing the new ram... but I'm here now. I can always send it back. If you need more info on my system, feel free to ask. Thanks for any and all help.