This is based off of the fact that you mentioned Assassin's creed earlier. Honestly a 390/970 is all you need, a 980 or 980 ti is meant for high resolutions.
EDIT~~~~~~~~~~ Not sure how well that MOBO will do with OCing, but I stuck an unlocked cpu in there just in case you ever wanted to OC.
PCPartPicker part list: http://pcpartpicker.com/p/7d6kNG
Price breakdown by merchant: http://pcpartpicker.com/p/7d6kNG/by_merchant/
CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($224.99 @ NCIX US)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($24.99 @ Micro Center)
Motherboard: Gigabyte GA-H97M-D3H Micro ATX LGA1150 Motherboard ($79.99 @ SuperBiiz)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory ($46.88 @ OutletPC)
Storage: Samsung 850 EVO-Series 120GB 2.5" Solid State Drive ($67.72 @ Amazon)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($51.88 @ OutletPC)
Video Card: MSI Radeon R9 390 8GB Video Card ($309.98 @ SuperBiiz)
Case: Fractal Design Define R4 w/Window (Black Pearl) ATX Mid Tower Case ($107.99 @ Directron)
Power Supply: EVGA 750W 80+ Gold Certified Fully-Modular ATX Power Supply ($89.99 @ Newegg)
Case Fan: Corsair Air Series AF140 Red 66.4 CFM 140mm Fan ($15.08 @ OutletPC)
Case Fan: Corsair Air Series AF140 Red 66.4 CFM 140mm Fan ($15.08 @ OutletPC)
Total: $1034.57
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-11-07 07:17 EST-0500