Im looking at getting a pre-built system for my little brother, he wants to start gaming on computer, I would like to buy the tower from Best Buy since i work there, and i can get 18 months no interest on my current credit card from there. My Budget on the tower is around 750 firm. Should i buy an i5 around 500 and just add a GPU and PSU? I don't have a CPU brand preference. He doesn't need anything crazy he is only 13.