I have recently installed a sapphire 7870 OC 2gb Edition into my system, i am currently running a AMD fx 6100 proccesor with a 500w *no overclocking* PSU with a ASUS m5a78l motherboard, i have been having problems playing wastlenaders on ARMA 2 reaching 9 FPS and getting 'magor' FPS drops during Battlefield 3 multiplayer. Is my pc bottlenecking and if so what shall i change to prevent this ?
Your CPU and graphics card seem fine, I would look into a higher speed RAM, and make sure you have at least 4GB in dual channel configuration. Another thing that would help is a faster hard drive, at least 7200 RPM or a Seagate momentus XT hybrid drive. I would also consider overclocking a bit, 500 Watts is more than adequate for a small 500 Mhz overclock on your CPU with a good performance gain.