The only reason I build my own is so I can do it a little at the time. It's hard to throw down $1100 at once, but slowly building up a new system $50-100 at a time isn't so bad.

If I had the money to blow, I'd go with a Dell XPS, hands down. Definitely the most bang-for-your-buck. Alienware desktops have a bit of a history for being horribly unreliable. They do have some nice laptops, though.