Yeah, single core CPUs are beating out the X2s at gaming, but I've read loads of reviews of the FX series going up against the X2 series, and well basically, the FX out preforms the X2s by a little in gaming, but we're still talking top end CPUs. So at this price bracket, you're not going going to see a MASSIVE difference in fps. Seriously, if your playing a game at around 70fps, and then you see one running at 90fps, you're not going to see much difference.
And the way the gaming market is going, a lot of new games will be using dual core technology to the full. FEAR is going to try and use it to the best of it's ability, and personally, if you want a good gaming computer that doesn;t need much upgrading, go down the X2 road. It's worth it.