Buying a Gaming PC, What to Do?

Hey,

I am going to be buying a gaming PC. I don't know how to build, but, I have a friend that I could pay to build it. Is it definatley worth building, or are there sites that have good deals on pre-built? Also, which sites are best for each?

-Thanks

mm if you want part advice pm me a budget and ill seek you out the best deals off the pair with some sweet saving(idk a $400 crysis on high rdy rig is pretty sweet).