I have an older pre-built HP Pavilion M8400F. not sure what the motherboard type is. It has an AMD phenom 9500 quad-core processor that I want to upgrade if at all possible. I have already taken out the original Nvidia graphics card and replaced it with a Nvidia 550 TI. I only play things like guild wars 2 right now but I want to get into some higher performance games. Would just like to know if I can upgrade the CPU and if so what are some recommendations.