Quadcore (Q6700) with 4 GB of RAM, 32-bit OS or 64-bit, plan on overclocking?

[Erikir]

I have a Dell XPS 700 with an EVGA GTX 470, Intel Core 2 Quad Q6700, and 4 GB of DDR2 (667 Mhz)

I will be using it pretty much just for FFXIV, but I'm not sure if the bit version of my OS matters?

I figured since I will be OCing, that 64-bit might be better and make more use of multiple cores?

Does the version matter?