Conclusion
Gaming at 4K Ultra HD is a visual treat if you can muster frame-rates of 60 fps and game developers are willing to add high-resolution textures that come to life at 4K. Don't fall for the "4K is useless at 28-inch" naysayers.
When sitting 2-3 feet away from the screen at a workplace, your eyes can tell things apart, the pixel pitch still around 150 dpi. The difference this makes to geometric imperfections in games with procedural/tessellated geometry is immense. A pair of GeForce GTX 980 Ti graphics cards should guarantee smooth gameplay at this resolution.
Intel's quad-core mainline platform continues to dominate gaming PC builds. Unless you're doing an abnormal amount of work simultaneously, the Core i7 HEDT platform is still overkill for this resolution.
Perhaps the greatest good that's come out of the advent of 4K is that prices of high-resolution monitors have come down. Before 4K, the highest single-monitor resolutions you could buy were 1440p and 1600p, and monitors from notable brands usually started at around $800, going well into four-digit figures. 28-inch 4K monitors can be had for as little as $449 if you look in the right place, but those come with TN-film panels. The next best thing is AMVA. ViewSonic offers a well-priced AMVA 4K monitor with 2 ms response time and IPS-like color-reproduction for around $650, making it an excellent choice for a display.
Below is the shopping list for your reference.
Could you have built a better machine that plays games at 4K? Tell us in the comments section!
Disclaimer: Prices are sourced from Newegg.com, don't include taxes or shipping, and are for hardware only. TechPowerUp encourages the use of genuine software.