Your motherboard will not allow you to overclock. You need a P67, Z68, Z75 or Z77 chipset motherboard to overclock LGA 1155. B75 will not do it.
As such I would keep the 2600 as the extra threads make it more powerful than the i5.
Oh.. On the their website it has OC Genie II @@
So i will stick with i7 2600...
thanks for your answer