The fastest cpu available for the 1155 socket that's supported by your motherboard is the i7-3770k. And it can be overclocked so that can give you some more headroom. A 'bottleneck' is something you will almost always have as either the cpu or the gpu will be faster given a certain piece of software. I would max out what you can if you want to stay with this platform or consider a complete platform upgrade if you can afford it. Either way, you'll have a bottleneck, and that's nothing to worry about as long as the system does what you need.