^+1, P67 would be more appropriate as you are overclocking. For overclocking you'll also want an aftermarket HSF - off that site the Hyper 212 is likely your best option. For the RAM get whatever set is cheaper. What PSU do you currently have? Just to make sure it will be sufficient.
Im using the Palit gts 450 sonic platinum.very good card.seems to run all my games on my BENQ G2222 HDL monitor at 1920 x 1080 resolution with all details set to ultra.Including the likes of crysis 2.Had a palit 9600 gt sonic prior to this and was so impressed with that card that i stuck with the company.im also using Kingston hyper blue ddr3 1600 ram ( 8gb of it as it a good price) for most games you will only need 4gb but some games utilise extra ram for reflections and shadows like Race Driver Grid for example and i think for other game companies this will become the norm.Good luck and enjoy your build.Regards.Kevin.
SLI / CF - this means adding a 2nd GFX card and linking them together ..... can increase performance sometimes very close to 100% though most games won't scale quite that much....average is 2 cards will do about 176% of 1 card. The P8P67 Pro will handle a 2nd card, tho you'll need a 750 PSU when ya do.