The PCI have a factor, you have a great card. I have 7970 normal edition and I run bf on high with 60fps, you have 16 gigs ram which you don't need that much for games, your CPU is not that bad, yea it will lower some of your settings but not as near as you described, that's why I am sayings it's your mobo. But if you run other games on high with no problems, then ignore my post, I am very sure of my opinion because I had your same problem, I remember when I bought the 7970 I had no improvement with bf3 the same as you are saying lowering makes little difference and lag at some places, so I bought an expensive mobo. So my performance increased to ultra with a lot more than 60fps, it turned out my PCI was very old an my CPU socket was not utilizing my CPU at full potential, that's why you have mobs for 10$ to 200$. But it's you choice. Tell me if you figured your problem I really want to know.