HDR monitors are not out yet, content is not out as in games rendering to the screen with High Dynamic Range. Basically HDR will give more life like intensity - for example looking at a camera flash on a HDR monitor would be like looking at a real one. The sun on the HDR monitor will actually be rather bright (not as bright as the sun but a lot brighter then current monitors). Most games internally render in HDR (better precision) and then tonemap to LDR (low dynamic range). Still the game will need to output to the monitor HDR.
Now should I spend $399 for a 4K freesync monitor or add $200 and get an Oculus Rift? Looking at VorpX that takes a number of games and makes them 3d with head tracking is very intriguing.
http://www.vorpx.com/supported-games/