Yeah, the only way I'd get a large high end laptop is if it didn't travel much at all. Negates the advantage of a laptop. 17"ers usually weigh too much to adequately support the frame when you're holding it. Creates lots of flex across the surface. And they're hard to keep cool if they're beefed up.
Alienware uses quality parts, but they focus too much on bling and lights. And you always overpay.
I wouldn't necessarily go after a gaming system. I'd build one that's similar minus overpaying for the graphics card.
Do you have the confidence to build your own?