I just recently switched out my NVIDIA GTX 750ti for a R9 270. So far there seems to be a huge issue with the HDMI port in that it won't display on my second monitor. I have the latest Crimson Edition driver, version 16.11.5.
I have two AOC 23.5 inch monitors that can support two HDMI and VGA. I use an HDMI to DVI adapter and a HDMI cable to connect HDMI. I am currently on Windows 10. I'd be glad if anyone has the solution for this!