For cpu atleast fx 8320/8350 or 4670k and a 1440p monitor, if you wan't to use r9 280x and wan't to get the best out of it. Any decent quality 500 or more psu is enough. Ram depends on the game requirements, but currently 8 gb ram is recommended. A pci-e 3.0 slot motherboard and an SSD for games like Battlefield 4.