an i5 is good for gaming. you only need the extra cores if you're streaming while gaming, or doing lots of video editing and rendering.
tweak:
PCPartPicker part list:
http://pcpartpicker.com/p/RBsqZL
Price breakdown by merchant: http://pcpartpicker.com/p/RBsqZL/by_merchant/
CPU: Intel Core i5-4590 3.3GHz Quad-Core Processor ($187.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($24.89 @ OutletPC)
Motherboard: ASRock H97M PRO4 Micro ATX LGA1150 Motherboard ($74.99 @ SuperBiiz)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($45.89 @ OutletPC)
Video Card: Sapphire Radeon R9 270X 4GB Dual-X Video Card (2-Way CrossFire) ($163.99 @ SuperBiiz)
Video Card: Sapphire Radeon R9 270X 4GB Dual-X Video Card (2-Way CrossFire) ($163.99 @ SuperBiiz)
Case: NZXT S340 (Black) ATX Mid Tower Case ($63.99 @ SuperBiiz)
Power Supply: Corsair Professional Gold 850W 80+ Gold Certified Fully-Modular ATX Power Supply
Total: $725.73
Prices include shipping, taxes, and discounts when available