I suggest waiting for a GTX1070 to become available (and for price gouging to stop).
Should stabilize about $430USD for the cheaper cards.
There are several improvements including asynchronous optimizations which will benefit future DX12 titles. Even if it doesn't add much FPS it can significantly improve STUTTERING in some cases (lack of preemption/asynchronous buffering causes stuttering in many current titles.).
Newer cards have VR optimizations, and GTX1070/1080 have a cool thing called Ansel which can take 2D or 3D snapshots in future, supported games.
Other stuff: HEVC, HDR, higher bandwidth improvements, lower power (may not care but it also means room temperature is lower)
The only other cards I recommend depend on your...