Im amazed to see so many people recomend the XPS over AlienWare. They are both expensive, yes, but an XPS is more Overpriced and has less choice when building, compared to AlienWare, and AW would just build you a better machine anyway. Dell XPS sucks, period. AW is expensive, but atleast they build you a machine with quality parts, that you would use if building yourself, and its totally upgradable just like if you build yourself.
I would NEVER even think about getting a Dell if I wanted a high end gaming rig. You people are crazy.