The motherboard does not affect the performance of a computer because it has no effect on the actual specs of the machine. However, with overclocking the computer's different parts such as the CPU and the GPU, that is where the motherboard has an effect on performance.

Do motherboards increase performance?

Motherboards dont generally up your performance. That motherboard only supports the 125w FX-8000's and not the FX-9000 225W so its not going to overclock well.

Is motherboard important for performance?

Motherboards are both extremely important and un-important at the same time. They are important because they provide the interconnectivity between the CPU/GPU/Ram/Storage/network - so without one nothing can be done.