Computer Freezing While Playing Games

I purchased a Computer from Cyberpowerpc and it freezes whenever I am playing games (WoW, Steam games, etc.) They suggested that maybe the graphics card was bad so they sent me a new one. Replaced it and still does it. Then sent them the entire computer back and they refurbished everything. Just got it back and it still does it. I've checked and updated the drivers, but other than that I am a computer novice. Please help me. I was wondering if it were a power supply issue? Is it too weak?

Here's my Setup:
BLUETOOTH: None
CABLE: None
CAS: NZXT Source 530 w/ USB 3.0, 10-port fan hub, Side-Panel Window
CASUPGRADE: None
CD: LG 12X Internal Blu-ray Drive & DVDRW, 3D Playback Combo Drive (BLACK COLOR)
CD2: None
COOLANT: Standard Coolant
CPU: AMD FX-9370 4.40 GHz (4.7 GHz Turbo) Eight-Core AM3+ CPU 8MB L2 Cache & Turbo Core Technology
CS_FAN: Default case fans
DOCKINGSTATION: None
ENGRAVING: None
FA_HDD: None
FAN: Asetek 550LC 120mm Liquid Cooling CPU Cooler - Extreme Cooling Performance (Single Standard 120MM Fan)
FLASHMEDIA: None
GLASSES: None
HDD: 2TB (2TBx1) SATA-III 6.0Gb/s 64MB Cache 7200RPM HDD (Single Drive)
HDD2: None
HEADSET: None
IUSB: Built-in USB 2.0 Ports
KEYBOARD: (Keyboard & Mouse Combo) Cooler Master Storm Devastator Gaming Keyboard & Mouse Combo (Black Color w/ Blue Light)
MEMORY: 16GB (8GBx2) DDR3/1866MHz Dual Channel Memory (Corsair Vengeance)
MIR_VCSSD: NONE
MONITOR: * 24" Widescreen 1920x1080 ASUS VS247H-P 1080P (23.6" Viewable) 2ms LED Backlight, DVI, HDMI Input [+179]
MONITOR2: None
MONITOR3: None
MOPAD: None
MOTHERBOARD: GIGABYTE 990FXA-UD3 AMD 990 ATX w/ Ultra Durable 3, On/Off Charge, GbLAN, 4 PCIe x16, 2 PCIe x1, 1 PCI
MOUSE: None
NETWORK: Onboard Gigabit LAN Network
NFC: None
OS: Microsoft(R) Windows 8.1 (64-bit Edition) + Office 365 FREE 30 Days Trial
OVERCLOCK: No Overclocking
POWERSUPPLY: 600 Watts - Standard 80 Plus Certified Power Supply - SLI/CrossFireX Ready
RAMDISK: None
RUSH: Standard processing time: ship within 5 to 10 Business Days
SERVICE: STANDARD WARRANTY: 3-YEAR [3 Year Labor, 1 Year Parts] LIMITED WARRANTY PLUS LIFE-TIME TECHNICAL SUPPORT
SOFT1: Microsoft(R) Office 2013 Home and Student (Word, Excel, PowerPoint + OneNote) [+119]
SOUND: HIGH DEFINITION ON-BOARD 7.1 AUDIO
SPEAKERS: Eagle Arion ET-AR302-BK 6 Watts RMS 2.0 Black Soundstage Speakers [+19]
TEMP: None
TVRC: None
USBFLASH: None
USBHD: None
USBX: None
VIDEO: XFX Double D AMD Radeon R9 280 3GB GDDR5 PCIe 3.0 x16 Video Card (Single Card)
WNC: PCI Wireless 802.11n 150Mbps Network Interface Card [+19]