there shpuld almopst be no benefits between 32 and 64 bit in wow since the new patch all the settings have been reset and changed. just play with it o and if you look under the slider that controll the FPS you could change the rendering from the wow client to 100% to 50% so less GPU and CPU stress
i used to have some major fps drops from stable to like 16 fps, but after a few updates i havent had any real issues sorry to hear you are having problems man, but mines running nicely
It sucks when we buy an expensive new faster machine that doesn't play as well as the old one. My motto is, "If it ain't broke, don't fix it!"