I have a pc that's pushing 7 years old. Single core processor, NVidia 8600 graphics card (that happens to be jury rigged for cooling since the fan fried on me a year and a half ago), and only two gigs of ram. The only issue I have had so far is some pretty severe lag in highly populated areas. But given what rig I am running I was expecting nothing less. I suggest taking a serious look at what your running and asking yourself where the problem really lies.
LOL...had to edit cause I said two megs of ram instead of gigs. Not enough coffee yet I guess.