First of all, calculating all the peripherals will leave him poorer by 20k. So that leaves us with 30k for MoBo+Proc+RAM+GPU. I’d suggest getting the AMD 790FX chipset based MoBo (10k), Athlon II X4 630/620 (8k), 4GB DDR3 RAM, ATI Radeon HD5750 GPU. Will make a balanced rig.