if you get an intel cpu with QUICKSYNC (intel gpu 600 series or higher), then you don’t really need a separate gpu.
if you want to go with AMD cpu, then you will need an nvidia gpu.
if your intention is to get into (or already have) 4k content, then please read entire thread @ Plex, 4k, transcoding, and you
finally, you probably can’t go wrong with going ‘super sized’ @ FreeBSD Enterprise 1 PB Storage