I don't have a specific model to recommend, but keep in mind the three key variables: The pixel density of the monitor versus its physical size versus the PPI settings available in your operating system.
On a Mac, you have 1x and 2x, which means a 27" 4K monitor will either show everything too small at 1x or too big at 2x, so go for a 24", which will be like a Retina version of the older 24" Cinema Display. On Windows 8, you have 1.0x, 1.4x, and 1.8x, so you'll probably be fine with 1.4x on a 27" or 1.8x on a 24".
On a Mac, you have 1x and 2x, which means a 27" 4K monitor will either show everything too small at 1x or too big at 2x, so go for a 24", which will be like a Retina version of the older 24" Cinema Display. On Windows 8, you have 1.0x, 1.4x, and 1.8x, so you'll probably be fine with 1.4x on a 27" or 1.8x on a 24".