Own an alienware, very happy with it. Sure you can get more bang for your buck if you make em yourself, but the alienware has a great internal structure with amazing cooling and whatnot. If you're lazy and want an plug and play option, no reason not to choose alienware. Gratz.
As far as the debate about who makes em';
Alienware operates separately from DELL, the only relation is monetary/distribution (at least according to their public statements). The Alienware products have not changed since DELL acquired them.