If you're going to re-use your HDD and DVD drive:

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i3-4130 3.4GHz Dual-Core Processor ($123.41 @ Amazon)
Motherboard: MSI H81M-P33 Micro ATX LGA1150 Motherboard ($44.99 @ Newegg)
Memory: A-Data XPG Gaming Series 8GB (1 x 8GB) DDR3-1600 Memory ($62.99 @ Newegg)
Video Card: PowerColor Radeon R9 270X 2GB Video Card ($215.91 @ Newegg)
Case: Cougar Spike MicroATX Mini Tower Case ($34.99 @ Newegg)
Power Supply: EVGA 500W 80+ Bronze Certified ATX Power Supply ($44.99 @ Amazon)
Total: $527.28
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-01-01 12:05 EST-0500)