if gaming is all you want from it then its overkill... thats not to say when the new consoles arive hyperthreading wont be usefull it might. but in general for todays games a 2500k or 3570k make more sense for your pocket as they will give exactly the same performance as a 2600k in games.
personally i prefer cpu's with hyperthreading as games is not all i do... if you do photoshop or 3dmax or similar and a bit of video editing then the 2600k will give a little more performance .