Here is the best value build with the same peformance you can get.
I assumed the cards were personal preference, but the EVGA SC cards will perform much the same, but at a slightly higher temperature with lower noise, not much to consider tbh.
Feel free to put the second card in the third slot if you want, provides additional airflow to the cards while giving the same performance, as they are both 8x slots.
PCPartPicker part list:
http://nz.pcpartpicker.com/list/KXFhtJ
Price breakdown by merchant: http://nz.pcpartpicker.com/list/KXFhtJ/by_merchant/
CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor ($549.00 @ 1stWave Technologies)
CPU Cooler: Noctua NH-D14 65.0 CFM CPU Cooler ($169.00 @ 1stWave Technologies)
Motherboard: Gigabyte GA-Z170X-Gaming 7 ATX LGA1151 Motherboard ($369.00 @ PC Force)
Memory: Kingston HyperX Fury Black 16GB (2 x 8GB) DDR4-2133 Memory ($119.00 @ 1stWave Technologies)
Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive ($148.00 @ 1stWave Technologies)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($118.00 @ 1stWave Technologies)
Video Card: EVGA GeForce GTX 1080 8GB Superclocked Gaming ACX 3.0 Video Card (2-Way SLI) ($1389.00 @ 1stWave Technologies)
Video Card: EVGA GeForce GTX 1080 8GB Superclocked Gaming ACX 3.0 Video Card (2-Way SLI) ($1389.00 @ 1stWave Technologies)
Case: NZXT H440 (Matte Black/Red) ATX Mid Tower Case ($229.95 @ Computer Lounge)
Power Supply: Corsair RMx 1000W 80+ Gold Certified Fully-Modular ATX Power Supply ($305.00 @ 1stWave Technologies)
Operating System: Microsoft Windows 10 Home OEM 64-bit ($164.00 @ 1stWave Technologies)
Monitor: Dell S2716DG 27.0" 144Hz Monitor ($1076.34 @ Aquila Technology)
Total: $6025.29
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-08-17 13:01 NZST+1200