This would be my pick:
PCPartPicker part list:
http://pcpartpicker.com/p/26oJd
Price breakdown by merchant: http://pcpartpicker.com/p/26oJd/by_merchant/
Benchmarks: http://pcpartpicker.com/p/26oJd/benchmarks/
CPU: Intel Xeon E3-1230 V3 3.3GHz Quad-Core Processor ($244.30 @ SuperBiiz)
Motherboard: ASRock B85 Pro4 ATX LGA1150 Motherboard ($74.99 @ Newegg)
Total: $319.29
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-21 12:14 EST-0500)
The 8 cores of an FX processor would also be good for video editing:
PCPartPicker part list:
http://pcpartpicker.com/p/mFN6
Price breakdown by merchant: http://pcpartpicker.com/p/mFN6/by_merchant/
Benchmarks: http://pcpartpicker.com/p/mFN6/benchmarks/
CPU: AMD FX-8320 3.5GHz 8-Core Processor ($154.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: Asus M5A99X EVO R2.0 ATX AM3+ Motherboard ($114.98 @ SuperBiiz)
Total: $295.96
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-21 12:15 EST-0500)
Personally I'd take the Xeon option.