Those 5870s are as good as Gold (Literally). You should be able to resell them on Ebay for a decent amount. They're considered to be the best Bitcoin capable GPUs (Performance/Watt).
As for the question... you won't notice a difference between a 930 and 2700K. I don't see a difference between a 3930K and i7 920 when gaming.
I notice the difference when I am processing complex workloads though... but you seem to be into gaming so none of that concerns you