[non-gamer]
The ultrawides are great in some cases. I'd go at least 2560x1440 though, and 29"+. I've never used a curved monitor but I've read that they had no negative effects for most people. I saw the LG 34UM68 on display in memex and it looked pretty darn good.
I upgraded to a 4k and love it, although it took some tinkering to get the dpi scaling proper. Text was quite distorted out of the box, but that may have been human error. I got the Samsung U28E590D.
I came from a dual 1080p setup and the 4k destroys it for my needs.
I can eat more hot wings than you.