Not going to happen, trying to fit a $300 part into a $550 build. Even though you already have some parts, there isnt much left to go round.
Also we need more info than that.
I assume your RAM is DDR3. Among these parts, if you don't go lower on the GPU, you can only skimp on the motherboard since higher priced MBs are more about specific features like more ports, USB 3.0, etc, things that shouldn't affect overall performance if you don't OC.