Got to get another i7 rig,Q6600 sits at about 80-90% ingame, some lag but, crazy fun!
My Q6600 is rocking it fine (3.4Ghz - 1080p with everything on High with 2AA), as it's a GPU dependent game - what GPU you running?
Also if someone else can confirm I think the i5 2500k is just as good for gaming, it's only really media encoding where the i7 show's its moneys worth.