Good 4K card for 2D / 4K Video Only. No Gaming...

If your not in a rush I'd wait for a 1050 or RX460. Low price and it should be good enough for 4k.
From the article:

Furthermore, along with these ports, there is also HDR support and support for the H.265 HEVC content compression codec. What’s interesting here is that currently, there are no displays with the DisplayPort 1.4 spec built into them but they are definitely on the way and the RX 480 is already prepared for their arrival.