Just a few answers:
The PSU requirements would be for the entire non-OCed system, and even then like PSU calculators, they tend to greatly overestimate to cover their own *** against someone buying a shady supply.
I think the laptop would be slower CPU wise if you don't take advantage of the hyperthreading, which many games won't (2.4ghz mobile cpu vs 3.5ghz desktop, I doubt even the newer architecture can overcome that big of a gap, especially if you OC the 3570k). Also, looking at GPU benchmarks, the 770M is (slightly) outpaced by the 7970M, the desktop 7970 is bound to be faster than both.
And to finish it off, the 780 should be fine, I don't see why it wouldn't work.