I would also get this CPU HSF Cooler over your choice, which is decent but in 6months to 1yr, it will not cool as good, so here is a CPU Cooler/CPU Combo.
1. XIGMATEK Dark Knight-S1283V: $44.98 Free Shipping*
Good suggestions all around. Actually the only real reason I'm putting in my two cents is because of how incredibly similar our two builds are.
My build is literally what you have with some minor changes here and there... That being said, I'm using an ASUS P6T Deluxe mobo.
I haven't had any real problems with it, and I love the bonus features ASUS throws in. Overclocking is a breeze; the board is smart and automatically adjusts various settings and timings to achieve a more stable OC. Though to be fair, I don't really know if EVGA or Gigabyte or others do similar things. The P6T Deluxe has made me a big fan of ASUS though, and they've earned my business until further notice.
See that, the Egg must be running low of OCZ am stock since alot of people ate buying them. Also with the OCZ Flex you posted, you do not that you might lose the usage of the 1st ram slot near the CPU when using an aftermarket CPU Cooler.