Sorry, I should have mentioned what i'm doing with my rig. It's for gaming 99% of the time only. Some multitasking while gaming might happen.
Cost on the ram is about the same. $300 for x2 6 gig kits vs $300 for 1 12 gig kit with 3 sticks.
I would really like to run my ram at the rated speeds of 1600mhz at 1T is possable. I have heard that running 1T or OCing your cpu might be problematic with all ram slots full. I have also heard that some bios don't work perfectly with 4 gig ram sticks.