If you're multiboxing a lot, I'm not sure if 5 or more game instances will run at @4k resolution with decent FPS, supposedly for some games multiple GTX 970's/980's are required just to run one client at 60 fps.
I had http://www.asus.com/us/Monitors/ROG_SWIFT_PG278Q/ in mind, GSYNC seems to be really cool, but it only activates in Fullscreen mode, so not its useful with Isboxer.