Mac Mini powerful enough to play any 1080p movie?
You won't do that with a Mac Mini. The latest Mac Mini uses a Haswell cpu (core gen4) which provides acceleration for H.264/AVC 8-bit, VC-1, MPEG2 and JPEG.

Additionally:

H.265 = HEVC = MPEG-H Part 2 = standard

x265 = encoder (and not the only one which exist).