The i5 will give you much more bang for buck than the i7, as the only difference between the two (as previously mentioned) is hyperthreading and a .1GHz clock speed difference. Neither of these are useful in gaming, and likely never will be. Hyper threading is exclusive to the i7, and it basically allows windows to see and extra 4 threads, making the i7 an effective 8 "core" CPU. However, very few programs can actually utilize these extra resources, and unless you are doing heavy video work and other multithreaded tasks, it is not worth the extra money. Also, I would recommend getting a Haswell i5 over any older CPU, such as an Ivy Bridge or Sandy Bridge CPU, mainly because they are only available for the 1155 socket, which is no longer supported. Going with Haswell provides an upgrade path, as it is brand new, and will support another CPU revision with the same socket. As for overclocking, it really isn't necessary. OC'ing is really only useful when your CPU begins to bottleneck your games, and the i5 4670k will not bottleneck for at least a couple years.