I don't know how to explain the lag issue. It's almost in every game I play, and the genre varies. So it's not limited to, say, and FPS or anything. I've gotten it in Skyrim and Assassin's Creed II. There's also other titles as well. Even though I can overclock the CPU, there's just some limitation that seems to bring performance down at times.
I do get the same performance with lower resolutions, so it could just be the CPU. I guess there's only one way to find out, lol.
Will update as soon as I install it.