Changing Power Supply in an Alienware Area51 ALX? is it an option?

Hey Guys!

Im back again, with sad news.
Basically, i recently had a huge success with getting the lights to work thanks to a couple of awesome guys here! So i figured this is the best place to come for advice/fixes. 

At the moment everything works on the PC, lights Fins.
Ive been trying to play Assassins Creed 4, at about 10 minutes into the game, it will instantly shut down like its over heating. and turn itself back on.
Does the same thing with other intensive games, Battlefield 4 being one of them.

Ive got HW monitor up on a second monitor and my CPU level isnt going about 35/40 degrees, and my GPU gets to around 75 degrees.

Are these bad temperatures? My graphics card MSI GTX 780 starts to make a squeal noise, its not too loud but loud enough, but ive heard that is coil whine? nothing to worry about? correct me if im wrong, im just going off things ive heard around places. Could it be a problem with the GPU?

I was told from another forum that its most likely a bad power supply and cant handle it, yet i find that hard to believe since Alienware's are built for high end stuff right? including the power supply?

Is it likely everything will work if i change the power supply, because i know about that 10 pin connector for the MIO board which isnt a standard thing...

I Just want to be able to enjoy my pc! :(

Thanks again for any help, super appreciated!