What GPU would you put with this build for Warzone?

[BloodyNine]

Current build is:

CPU: Intel Core i7 6700K
Mobo: ASUS Maximus VIII Hero ATX Motherboard
RAM: G.SKILL Ripjaws V Series (8 GB x 2) DDR4 3200 MHz CL14
SSD: Samsung 970 PRO 512 GB PCIe NVMe M.2 (MZ-V7P512)
CPU Cooler: Cooler Master Hyper 212 RGB Black Edition
PSU: EVGA SuperNOVA 650 P2, 80+ PLATINUM 650W
Case: FRACTAL DESIGN Define R6 Tempered Glass ATX PC Case - White

I mainly play Warzone, any advice on what GPU I should get?

TIA

 

[BloodyNine]

1920 x 1080
240hz
Not upgrading from anything, I got this build from a mate but he kept the GPU

 

[BloodyNine]

About £350