Honestly, if I were you, I would just go to Voodoo PC and buy one. This is CAG and I know most people will tell you to build your own PC, but as someone who does it pretty regularly, if you really wanted to build your own PC, you would have thought to do it already and not waited for these guys to tell you.
Yes, you will save money building your own, but if you are new at this and you have a pretty high budget, you are better off just purchasing a pre-built one.
If you don't know what you are doing it can be a real pain in the ass, and the first time you have to RMA a motherboard because you jammed in the RAM backwards, you are going to kick yourself and say, "If I got one pre-built, I'd be playing Oblivion right now."