This is my current system in an Antec 900 with noisy fans. Most I can get is 30-40 FPS on low-med setting 1680x1050 open beta BF3. RO2 can only handle 40 on low settings 1680x1050. Recently replaced a fried motherboard and video card, so was hoping to upgrade cpu and or ram (my water cooler is overclock friendly). Also need 4 of the quietest 120mm fans(I like lights/uv reactiveness) and a 5 fan controller.
If you are not going to get another MB and you are not going to over clock then...What is your OS ? 32bit or 64bit , it makes a difference on the ram amount.
I have vista 64 which I just reinstalled because of new mother board. I want the most performance I can get for $250 or around there. Looks like I'll be playing BF3 on lowest settings but a steady 60fps should be attainable.