You can't just change the CPU the way you indicate - you will also have to change the motherboard.
I doubt it will have as much impact on your gaming as you are hoping for. Your graphics cars seems to be a weak point as well.
You can save substantial money by going to an Intel Core i5 series instead (still a change in motherboard) and then spending the saved money on upgrading your video card.
Or even better - if there is a better AMD CPU that is socket-compatible with your current mobo, get that and apply all the savings to upgrading your video card.