@Poster I've never been too fond of Dell's customer service. You could also probably get better parts for cheaper, and the rigs come pre-installed with whatever version of Windows, and knowing Dell, they probably load a lot of unnecessary stuff on it, which eat resources, defeating the purpose of a gaming computer. I'm not saying you should absolutely hate Alienware/Dell, but I'm just saying, if you want to maximize power per dollar, building it yourself is the best way to go. It's not extremely hard, either. If you're worried about ruining it, then take it in to a computer store. They'll probably build it for you, and it'll probably end up being cheaper than buying a computer from Alienware.
Then again, I prefer having total control of my system.