I've made the jump to 4k with this AOC monitor, and it's build and image quality are exceptional for the $279 I spent on it (and Tom's Loves it: http://www.tomshardware.com/reviews/aoc-u2879vf-28-inch-4k-uhd-freesync-monitor,4575.html)
Though, I am now tasked with needing an adjustable second...