Building a PC

So I've decided my toaster isn't enough for me anymore and i want to play like a big boy. I have very little idea what im doing and when i set this up i only had a few things in mind.

• get atleast 6 cores ( i know 4 is fine but i personally wanted 6 to be extra k
• 8 GB of ram ( pretty sure this is standard )
• DO NOT SKIP ON POWER SUPPLY ( i think i went a bit over board here )

Please rate and give idea on what a should change.

Minus my keyboard mouse speakers window 8.1 the actual computer should cost about 621.43$ im not looking to go to far over that