Gigabyte-GA-970A-UD3P.
PCPartPicker part list: http://pcpartpicker.com/p/zWWsXL
Price breakdown by merchant: http://pcpartpicker.com/p/zWWsXL/by_merchant/
Motherboard: Gigabyte GA-970A-UD3P ATX AM3+ Motherboard ($74.99 @ Newegg)
Total: $74.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-17 11:04 EDT-0400
You also might wanna consider getting a better CPU,because the FX-4100 isn't exactly for serious gaming and it is bottlenecking you GTX 770.
PCPartPicker part list: http://pcpartpicker.com/p/ZhVQD3
Price breakdown by merchant: http://pcpartpicker.com/p/ZhVQD3/by_merchant/
CPU: AMD FX-8320 3.5GHz 8-Core Processor ($139.97 @ OutletPC)
Motherboard: Gigabyte GA-970A-UD3P ATX AM3+ Motherboard ($74.99 @ Newegg)
Total: $214.96
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-17 11:09 EDT-0400
You can also go this way:
PCPartPicker part list: http://pcpartpicker.com/p/4r9sK8
Price breakdown by merchant: http://pcpartpicker.com/p/4r9sK8/by_merchant/
CPU: Intel Core i5-4440 3.1GHz Quad-Core Processor ($174.99 @ SuperBiiz)
Motherboard: Asus H81M-D PLUS Micro ATX LGA1150 Motherboard ($44.99 @ Newegg)
Total: $219.98
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-17 11:08 EDT-0400
The 4440 will be a perfect match for your GTX 770.AND the 4440 is stronger than the FX-8320.