Which combo would be better for pure gaming? Im not entirely sure how to overclock and how much performance it gives but is more cpu power worth it in exchange for less gpu power? BTW i can just fit a Cooler Master Hyper 212 EVO into my budget for overclocking
If your motherboard and power supply would be sufficient for Crossfire, I would go with the 3570k, which is actually very easy to overclock. 4.5GHZ can be easily achieved with minimal knowledge now days.
Then when you have the money for a second 7870, crossfire them for a beastly gaming PC.