I have the Sharp 4K monitor that Apple sells in its stores and it's incredible. I run it at retina resolution at 60hz (now possible on Mac OS 10.9.3+) with a Mac Pro and it looks amazing.
Very pricey, but in my experience, worth every dollar.
Sharp is a pretty big Japanese company. They rarely make own-brand consumer stuff for markets outside Japan though, which is why you haven't heard of them. http://en.wikipedia.org/wiki/Sharp_Corporation
Very pricey, but in my experience, worth every dollar.