^i dis like MIR's also, with this build alone i had 2 rebates that were not honored with a total of $75 that i did not get back, which really ****ed me off. So try to avoid them as much as possible.
overclocking is not going to yield this tremendous gaming improvement with that rig...it will do fine with no OC.
overclocking is fun, though.
overclocking your gpu may increase your framerates a little.