Changed the PSU in your build:
PCPartPicker part list:
http://pcpartpicker.com/p/76yxVn
Price breakdown by merchant: http://pcpartpicker.com/p/76yxVn/by_merchant/
CPU: AMD Athlon X4 760K 3.8GHz Quad-Core Processor ($80.98 @ OutletPC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($28.99 @ Micro Center)
Motherboard: ASRock FM2A55M-VG3+ Micro ATX FM2+ Motherboard ($44.98 @ SuperBiiz)
Memory: A-Data XPG V2 8GB (2 x 4GB) DDR3-1866 Memory ($76.99 @ Newegg)
Video Card: PowerColor Radeon R9 270 2GB TurboDuo Video Card ($149.99 @ Newegg)
Case: Apex SK-393-C ATX Mid Tower Case ($25.60 @ NCIX US)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($44.99 @ NCIX US)
Total: $452.52
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-10 14:58 EDT-0400
Btw buying 1866MHz RAM with CAS 10 is like 1600MHz with 9. For gaming, 1600MHz RAM is sufficient.