My computer freeze when i play games as fx. League of legends and CSGO

[W8zT]

Hey every one. i have a problem with my pc, and i was hoping that you could help me fix it. When i play games such as League of legends or CounterStrike Global Offensive my computer have theses random crashes. every thing freezes and my sound goes all scrachy, and i have to restart my pc manually to get it up and running again. and sometimes it has trouble starting up again.
¨
at first i thought it was a problem with the heat, but i'm not sure. ohh and btw this is a new pc i build myself, with some help, it costed me around 2000$ to build, and i've had it in like 3-4 monthes, how ever this problem occurred to me a few months back.

What i noticed was that i was still able to play HearthStone and Runescape, but more or less everything else crashed for me. this is including: Diablo III, League of Legends, Borderlands 2, Minecraft and also CounterStrike Global Offensive. there is probably some games i've forgotten too.

Specs:
MSI GeForce GTX 780 Gaming 3GB PhysX - "Twin Frozr IV", with WATCH_DOGS

Corsair H80i Hydro Series CPU Cooler

Intel Core i5-4670K - Socket-LGA1150, Quad Core, 3.4GHz, 6MB, 84W, HD460

ASUS MAXIMUS VI HERO, Socket-1150

Kingston DDR3 HyperX blu 1600MHz 2x8GB

Kingston HyperX 3K SSD 240GB 2.5"

Seasonic 650W gold edition

I really hope that you can help me out here.

 

[MPN]

Im not sure, but i have a feeling that Your PSU might be to weak for Your build.
On Geforces own website they say that the minimum recommended system power is 600w. And pluss the other Components 650w PSU might be to weak during heavy load.

Im not sure that is the problem as i have little to non knowledge in this area, but that is what comes to my mind.