Under 800$ :
PCPartPicker part list:
http://pcpartpicker.com/p/ofSq
Price breakdown by merchant: http://pcpartpicker.com/p/ofSq/by_merchant/
Benchmarks: http://pcpartpicker.com/p/ofSq/benchmarks/
CPU: Intel Core i5-3470 3.2GHz Quad-Core Processor ($184.99 @ Newegg)
CPU Cooler: Zalman CNPS5X Performa CPU Cooler ($14.99 @ NCIX US)
Motherboard: ASRock H77 Pro4/MVP ATX LGA1155 Motherboard ($87.55 @ Newegg)
Memory: Patriot Viper 3 8GB (2 x 4GB) DDR3-1600 Memory ($28.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Newegg)
Video Card: Gigabyte Radeon HD 7950 3GB Video Card ($289.99 @ NCIX US)
Case: Antec Three Hundred Two ATX Mid Tower Case ($49.99 @ Newegg)
Power Supply: XFX 550W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($53.99 @ NCIX US)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($15.98 @ Outlet PC)
Total: $776.46
(Prices include shipping, taxes, and discounts when available.)
Under 900$ :
CPartPicker part list:
http://pcpartpicker.com/p/ofV6
Price breakdown by merchant: http://pcpartpicker.com/p/ofV6/by_merchant/
Benchmarks: http://pcpartpicker.com/p/ofV6/benchmarks/
CPU: Intel Core i5-3570K 3.4GHz Quad-Core Processor ($219.99 @ Amazon)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($26.29 @ NCIX US)
Motherboard: ASRock Z77 Extreme4 ATX LGA1155 Motherboard ($124.99 @ Amazon)
Memory: Patriot Viper 3 8GB (2 x 4GB) DDR3-1600 Memory ($28.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Newegg)
Video Card: Gigabyte Radeon HD 7950 3GB Video Card ($289.99 @ NCIX US)
Case: Antec Three Hundred Two ATX Mid Tower Case ($49.99 @ Newegg)
Power Supply: XFX 550W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($53.99 @ NCIX US)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($15.98 @ Outlet PC)
Total: $860.20
(Prices include shipping, taxes, and discounts when available.)