All great 27-inch monitors have great picture quality, 27-inch minimum panel size and 2560×1440 minimum resolution. They also have at least IPS (In plane switching) panels instead of TN (Twisted Nematic) panels, which are of lesser quality. 

We would like to remind you that all professional monitors are overkill / over spend unless you’re a graphic designer, filmmaker, photographer, or a serious gamer with lots of money. And always use your monitor’s sRGB mode (if it exists), which matches your monitor’s colors to the most common color standard in use nowadays. Avoid  all other modes you’ll find on a monito, such as game, movie, reading, etc, which only hurt your picture quality rather than improve it.

The best 27-Inch Monitor: Dell UltraSharp U3415W (21:9, 3440×1440 display, able to work with multiple computers at the same time, ultra-thin bezel, lots of display connections, USB 3.0 hub, a stand with a wide range of tilt, swivel, height, and rotation adjustments.)
The best affordable 27-inch monitor: BenQ GW2765HT (with a good IPS display)
The third best 27-inch monitor: Dell's P2715Q  (4K monitor)
The best ultrawide 27-inch monitor: Dell UltraSharp U3415W 34-Inch Curved LED-Lit Monitor (all the benefits of a dual-monitor setup without ugly bezels splitting the picture in half. )