That's not even minimum settings, there are particle effects and other stuff that can be disabled on top of that. Using the config from this post I get well over 100 FPS when there's nothing going on, and dips down to about 40-50 if there's a lot of action and I can see a large area of the map. Because my heatsink is fucking huge and the air flow in my case is excellent.
The CPU and GPU are overclocked, but not to the point where I require a fan on my heatsink. I have an old machine somewhat similar to yours with a quad-core phenom II (actually an x3 740 BE with a core unlocked), 4GB of RAM and a GTX 460 1GB.
