Need Help! Overclocking Radeon 4870!

[xerb]

So I have the Sapphire Radeon 4870 512mb (old version). I bought the Arctic Accelero Xtreme Plus and my temps are...
Core:
Idle-30C
Load-40C
Memory:
Idle-40
Load-47C
My stock speeds are core-750 memory-900. If I overclock to core-850 and memory-1200 will I notice an FPS change in games like Crysis 2 on 1440x900 resolution? On stock speeds I get around 60 fps on gamer and around 40 maxed out. I want to aim for 60 fps maxed out...any suggestions

AMD Phenom X4 955 3.2 GHZ (i can easily overclock to 3.9 GHZ)
4GB DDR3 RAM
Radeon 4870 512mb
600w Pwr Supply
Zalman S series 64 GB SSD

Thanks, sorry for my english XD

 

[xerb]

oh ok thanks!

 

[xerb]

Best answer selected by xerb.