Hi I want to upgrade the graphics card in my sons pc (model above) to a NVIDA Geforce GTX 750ti. In order to do that I also need to upgrade the PSU. Can anyone help with what power PSU is needed? I am looking at the Corsair CXM500, would this fit and would it give enough power? Any other graphics card/PSU combination that anyone would recommend? I am buying them for Christmas so will probably be installing Christmas morning so need to get it right before hand