The bottleneck is game dependant no matter what graphics card you use if the game is meant for quad cores or more then you will be botllnecking the gpu. the 750ti is the most anyone should spend with a low end cpu though as stated. But playing multiplayer games like bf4 or battlefield or anything cpu bound a dual core will bottleneck. There are games that wont even load without modding unless you have atleast a quadcore like farcry 4 so the term bottleneck is really subjective