About as cheap as I could get it and keep the RGB RAM (though you could drop that to save some $$$ or spend more and get a mobo with RGB):
CPU: AMD - Ryzen 7 1700 3.0GHz 8-Core Processor ($304.89 @ OutletPC)
Motherboard: MSI - B350 PC MATE ATX AM4 Motherboard ($84.33 @ OutletPC)
Memory: G.Skill - Trident Z RGB 16GB (2 x 8GB) DDR4-3000 Memory ($134.99 @ Newegg)
Storage: Kingston - HyperX Fury 120GB 2.5" Solid State Drive ($56.00 @ Amazon)
Storage: Western Digital - Caviar Black 1TB 3.5" 7200RPM Internal Hard Drive ($65.99 @ Amazon)
Video Card: EVGA - GeForce GTX 1070 8GB FTW Gaming ACX 3.0 Video Card ($379.99 @ Newegg)
Case: Corsair - Carbide 400C ATX Mid Tower Case ($74.99 @ Newegg)
Power Supply: Corsair - RMx 650W 80+ Gold Certified Fully-Modular ATX Power Supply ($104.98 @ NCIX US)
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-05-25 15:14 EDT-0400
I can build an i7 based one as well, but it'll cost more. And I put in a bigger PSU than you need to make sure you have overhead to run RGB fans, controllers, strips, etc.
You could also save money by getting a 1060 6GB or (I'd recommend) an RX580 8GB.