As you want to use it for gaming and if you can stretch your budget little more then I would recommend you to get two sticks of 4 GB because it will enable the dual channel memory mode, that doubles the original memory bandwidth. ....
im okay with getting 2x4 gb i came here cuz there are so many of em and im not positive which one is compatible and the best deal with my current set up
Ya, it will be compatible with your current ram and you can enable the dual channel memory mode. Now you have 4 sticks of ram and you can overclock it to 2133 mhz in bios......