Don't bother getting an ultra powerful machine if you actually want to run it as a laptop - that is, from a
battery. My laptop is a modest, but still decent spec (2.1GHz Core 2 Duo + 1GB RAM + generic integrated video) and I can just about squeeze 4 hours of battery out of it.
I can't imagine much more battery with the specs you're looking at, which may render it useless as a mobile machine
EDIT: Your screen, and the GPU (especially with the 1GB GDDR in the GPU, which means continutal power required for main memory + the GPU's. Whilst that isn't much power, it stacks up over time, especially off of a chemical cell) are going to especially power hungry. Not so sure about the processor.
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