i7-4770k using integrated GPU: 4k@60, no issues.
EVGA nVidia GTX 750Ti: 4k@60, no issues.
i7-2600k using integrated GPU: 4k@60, no issues.
G540 Celeron CPU (2013 CPU) using integrated GPU: 4k@30 no issues, 4k@60 a slight slowdown during high action scenes. CPU was pegged @ 100% for majority of the scenes. I believe that this chip is using the same integrated GPU as the 2600k, so it may have simply been an issue of the performance capabilities of the chip.
EVGA nVidia GTX 680: 4k@60, no issues.