A CPU upgrade will make a huge difference if you're talking BF3 multiplayer. I upgraded from an FX-6300 (overclocked) to an i7 4770k and went from 45-70fps to 65-120fps with an AMD 7870 LE. I hit the minimum fps a lot less as well. With the FX I would mostly hang around 55-60, but would dip into the lower 50's quite often on certain maps. With the 4770k, I very rarely hit my lows, and usually hang around 80-90 fps on most maps. If you can, you should grab an FX-8320 or 8350. Large multiplayer games are extremely CPU dependent.