Do you need an OS? And is it $500 MAX or about $500. If there is a few more dollars to through at it, could make the difference in an i5 build or an i3 build.
http://pcpartpicker.com/p/BRMbYJ/by_merchant/
CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor ($176.95 @ SuperBiiz)
Motherboard: ASRock H97 Anniversary ATX LGA1150 Motherboard ($69.89 @ OutletPC)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-2133 Memory ($49.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($52.49 @ OutletPC)
Video Card: Sapphire Radeon R9 270X 2GB Dual-X Video Card ($124.99 @ Newegg)
Case: Apevia X-SNIPER2-WHT ATX Mid Tower Case ($49.99 @ Mwave)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX...