Building a Custom PC - need some suggestion?

Well it really depends how your budget really but the I5 really is the best bang for your buck for a gaming PC I would go with a i5 2500 or 2500k if your wanting to overclock it and spend the $100 on other components like a better mobo. There isn't a much diffrence from a i5 stock 2500 to a i7 2600 but if you can I would recommend getting the i5 2500k which means you can overclock it.