What Apple did was pretty amazing - I'm looking forward to the next iteration of their TB Display. I held out for over a year waiting for Apple to get off their butt to update their TB monitor. Sigh. But, I did tire of waiting, however, and here's how I spent my cash:
$525 on a Dell P2715Q, $175 on a Herman Miller Flo arm, $14 on a copy of SwitchResX, and $299 on Grado SR325e headphones (which I can plug into the P2715Q's output jack.
For a few more bucks than the outdated Apple TB monitor I got a 4k monitor that can put anywhere on my workstation courtesy of the Flo arm and killer cans that put any monitor's speakers to shame.