I am a huge fan of Sager/Clevo laptops. Unfortunately at the moment, they don't have any offerings with dual GPU setups, so they don't have much that would match/beat the M17 in performance.
Don't get me wrong, it will be a solid performing system. I am just a little wary about flaky support from Alienware.
Also, here is the same system, sold by a different company: http://www.xoticpc.com/force-extreme-built-flextronics-arima-w840-ocznbim17a-w840di-p-2495.html