It's really easy. Especially with today's tech. But if you want to buy pre-built (which I am also a fan of) there's plenty of sites that you can customize.Quoting Idioteque Stalker (view post)
If you'd like to try building, this amount of money can get you a sweet rig. ($812) I'd go for the sweet spot at a minimum though.
A comparable build (pre-built) would cost you $959.
How much you willing to spend?