Are you just looking for responses from people who chose to build a dedicated HTPC? I currently just have my PC (which I also use for other purposes including gaming). I use AMD/ATI graphics, but my video card (Radeon HD6850) is probably overkill if you are just looking to do video playback. I don't want to screw up your data set if you're only interested in responses from the perspective of what people used in a dedicated HTPC.
Was an AMD guy for many years but the last 2 builds I put together I went to Nvidia. Updates on a regular basis.
Paul
Custom ASUS Maximus X Hero, 16 GB Memory-ASUS GeForce 1050 Ti, H115i Pro AIO, 850W PS, CM H500P case, Corsair Vengeance RGB Ram, Samsung 970 EVO, HDHomerun Prime & Extend Tuners- running Windows 10 (and other goodies)