PCPartPicker part list:
http://pcpartpicker.com/p/3t7MXL
Price breakdown by merchant: http://pcpartpicker.com/p/3t7MXL/by_merchant/
CPU: Intel Core i5-4430 3.0GHz Quad-Core Processor ($179.98 @ OutletPC)
Motherboard: Asus H81M-D PLUS Micro ATX LGA1150 Motherboard ($44.99 @ Newegg)
Memory: G.Skill Ripjaws Series 8GB (2 x 4GB) DDR3-1600 Memory ($72.00 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($53.98 @ OutletPC)
Power Supply: Corsair Builder 600W 80+ Bronze Certified ATX Power Supply ($34.99 @ Newegg)
Optical Drive: LG GH24NSB0 DVD/CD Writer ($13.99 @ Newegg)
Total: $399.93
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-09-14 09:57 EDT-0400
I would have liked to upgrade the i5 to a xeon quad core with hyper threading which would increase the costs by around $30. But if you only plan on playing LoL, then this would work fine. It would also be nice to be able to upgrade the GPU later on, so I included a 600 watt power supply.