I've been doing extensive research in the more portable gaming offerings.
In terms of the most power for the size, your main options are:
MSI GS40 (1.85kg)
Good spec (6700HQ + 970M) in a thin and light case, with an good screen (good brightness, average blacks, average contrast, good colour after calibration) at an average price. 2 year warranty.
Hot and noisy though, with a sub-standard keyboard.
Gigabyte P34W V5 (1.81kg)
Good spec (6700HQ + 970M) in a thin and light case, with an average screen (average brightness, below average blacks, below average contrast, average colour, even after calibration). Runs a bit quieter and cooler than the GS40. 2 year warranty.
Pricier than the GS40. No thunderbolt or Displayport.
Aorus X3 (1.8kg)
970M in a thin and light case. Looks nice (if that matters). 2 year warranty. Cools better with no throttling when compared to the GS40 and P34W.
Pricier than the GS40 and P34W. Poor screen (good brightness, poor blacks, poor contrast, average colour). No 2.5" slot. 4th gen cpu.
Alienware 13 (2.05kg)
Very good build quality at a decent price.
Heavier and thicker than the competitors. ULV i7 and 960M limit performance. Screen brightness very low unless you opt for much pricier QHD panel. Only 1 year warranty.
Clevo P640RE (2.2kg)
Configurable even up to a 6820K with 970M. Cheapest of the lot for the specs. Good screen (average brightness, great blacks, great contrast, average colour).
Bulkiest of the options. Throttles a bit if not kept cool. Poor battery life. Slowest display response time (so not for 'pro' fps gamers).
There is no perfect machine. They all have their pros and cons, you just need to decide which are the most important for you.
I opted for the Clevo in the end as I wanted good contrast, wasn't fussed about battery life or portability, and it was the cheapest