This should be a good build for your brother.
PCPartPicker part list:
http://pcpartpicker.com/p/1suz5
Price breakdown by merchant: http://pcpartpicker.com/p/1suz5/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1suz5/benchmarks/
CPU: Intel Core i5-3570 3.4GHz Quad-Core Processor ($194.99 @ Newegg)
Motherboard: MSI B75MA-E33 Micro ATX LGA1155 Motherboard ($57.23 @ Outlet PC)
Memory: GeIL EVO Veloce Series 8GB (2 x 4GB) DDR3-1600 Memory ($53.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($59.99 @ NCIX US)
Video Card: Asus GeForce GTX 660 Ti 2GB Video Card ($216.98 @ SuperBiiz)
Case: Silverstone PS08B (Black) MicroATX Mid Tower Case ($34.90 @ Amazon)
Power Supply: OCZ Fatal1ty 550W 80 PLUS Certified ATX12V / EPS12V Power Supply ($29.50 @ Newegg)
Optical Drive: LG GH24NS95 DVD/CD Writer ($15.98 @ Outlet PC)
Total: $663.56
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-15 23:51 EDT-0400)