Awesome mod Mr. Fox!
I know this thread is dated now, but for others who are curious, a very easy and straight forward mod. Most importantly, relatively CHEAP.
I have a M15x (owned new since 2010) and after having a 970m for a year, I upgraded to a 980m, the 10-15% gain was enough of an itch for me. The only problem was the 980m would trip my 240 psu constantly with any attempt to OC (svl7/johnksss vbios). So I purchased another 240 psu and made the mod - now no more tripping!
For those with a AW M15x, a dual 240w psu mod is plenty and even easier to construct than the 330w mod, as the 240 psu's have only 1 black, 1 white, 1 green/blue wire..I didn't even have to solder anything!
Now my laptop has more than enough power