Ok, chugalug has gave you one option with i5+GTX 1080+HDD. They are good for now since i5 can still hold against current game with several tweak to optimized the game (such as turning down resolution scale in BF1).
My option was using i7+GTX 1070+SSD. The gpu is weaker, but you will be freed of cpu upgrade until the end of this build life. You do not have to tweak around to optimized any game that demanded up to 8 thread cpu (BF1 demand 6 thread, Mafia 3 and watchdogs 2 also demand more than 4 thread, just look around for games that were titled i5 killer).
For me SSD is a must have. SSD will save a lot of your life time used to wait in loading. I think our life is much more precious than anything. This SSD is just average SSD as the budget not allowed me to get you the best SSD which is Samsung 960 pro (or even evo series). But this average SSD is already 3x (or more) faster than any HDD. The 960 pro is 3x faster than average SSD, but the price just too much.
The psu will be able to support any single gpu you can throw in. When you feel GTX 1070 has no longer enough for you, then you can replace it with any gpu in the future without having psu and cpu as your limit.
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i7-7700 3.6GHz Quad-Core Processor ($297.99 @ SuperBiiz)
Motherboard: ASRock B250M-HDV Micro ATX LGA1151 Motherboard ($66.98 @ Newegg)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2666 Memory ($99.97 @ Jet)
Storage: Sandisk Ultra II 480GB 2.5" Solid State Drive ($132.94 @ Jet)
Video Card: Gigabyte GeForce GTX 1070 8GB Windforce OC Video Card ($379.00 @ Jet)
Case: BitFenix Nova ATX Mid Tower Case ($22.99 @ NCIX US)
Power Supply: SeaSonic S12II 620W 80+ Bronze Certified ATX Power Supply ($48.99 @ NCIX US)
Total: $1048.86
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-03-06 21:55 EST-0500
Good luck with your build