I wanted to update with an answer. I ended up getting an LG 27UD68 (4K, IPS, 10 bit, 60Hz Freesync). I got it for $349 BNIB, a pretty solid deal on a 4K monitor. While Freesync is useless for me, it did overclock with no tweaking up to 74Hz, a nice boost over the stock 60Hz. The colors are great, with it being 10 bit IPS it is a major upgrade over my old 21.5" ASUS TN (which was also a 60Hz panel). So far I've only had time to try a few games on it: Rocket League, Doom (2016), BF4, and Project Cars. With the exception of BF4, everything else that I have tried (though limited) has been beautiful on 4K with ultra settings. BF4 ran at about 30FPS, not exactly ideal.
 
For productivity it's a massive change, both because of physical real estate and the pixel real estate it has. It gives me room to do quite a bit more on the single screen. I may have to eventually look at getting another to work on. I will saw, the thin bezels are also very nice to have, and it's a very slim monitor with the power supply being an external brick. The stand is a bit wobbly, and I'd like to get a VESA mount for it to fix that, but overall I'm very happy with it.