Skimps :
Arc911 :
i would check the temps and clockspeeds of the cpu first when you get 40-70 fps to make sure its not thermal throttling
What's thermal throttling?
When your cpu gets too warm it slows itself down to protect itself. By slowing down it cools itself off.
Run this program in the background it will tell you the minimum and maximum of all your peripherals after a game.
Hardware monitor
http://www.cpuid.com/softwares/hwmonitor.html