Best gaming build for $900?

Hey there,
could you guys help me put together the best possible gaming rig for about $2000? Can I do better than this build for that kind of cash:
Intel Core i5-7600K, 3.2Ghz, box cpu
ASUS Prime B350M, AM4
Seagate BarraCuda 1TB (3.5", 1TB, 32MB, SATA III-600)
Patriot Viper4, 3000Mhz, 8GB (2x4GB), CL16
EVGA 450W, 80+ Bronze
Zalman Z1, USB3.0 black, 2x120mm
Kingston 120GB SSDNow UV400 SATA 3 2.5 (7mm height), EAN: '740617252866
Inno3D GTX 1050TI Twin X2 4GB GDDR5
What's the best way to get an OS? Is it okay to just grab it via torrent?...

EVGA 450W
Western Digital Blue 1TB
Western Digital Blue 1TB in a Cooler Master case, maybe?
The ADATA Ultimate SU650 240 GB.
Crucial Ballistix Sport LT Gray 8GB DDR4-2666
Intel Core i5-7600K
ASUS GeForce GTX 1050 Ti 4GB
MSI B350 Gaming Pro

~$2.00 UziShop

You can usually find pretty cheap activation codes for macOS lying around online.

You grab Windows straight from Microsoft via their media creation tool. As for activation, you can either buy a key officially or... well, you know how people handle that.