PCPartPicker part list:
http://pcpartpicker.com/p/k8cmmG
Price breakdown by merchant: http://pcpartpicker.com/p/k8cmmG/by_merchant/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($118.00 @ Amazon)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: Gigabyte GA-970A-UD3P ATX AM3+ Motherboard ($73.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory ($88.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Amazon)
Video Card: Sapphire Radeon R9 270X 2GB Dual-X Video Card ($169.99 @ Newegg)
Case: Rosewill Galaxy-03 ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($55.98 @ SuperBiiz)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($19.98 @ OutletPC)
Operating System: Microsoft Windows 8.1 (32/64-bit) ($102.52 @ NCIX US)
Monitor: BenQ GW2255 60Hz 21.5" Monitor ($107.60 @ Amazon)
Keyboard: Logitech MK120 Wired Slim Keyboard w/Optical Mouse ($14.98 @ OutletPC)
Speakers: Logitech S120 2.3W 2ch Speakers ($8.49 @ Amazon)
Total: $857.48
Prices include shipping, taxes, and discounts when available
Since you're budget is between 800-900 I made this. This will run all, if not most, games ( including BF4 ) at their highest settings. You can OC the 6300 if you want to and this mobo lets you do that. Also good upgradabilty for the future