is your pms on windows or linux?
if linux and you want to do 4k now or in the future, I would recommend you look for a video card with the most video ram, that is within your budget.
on linux, video ram is the bottleneck for 4k transcodes (about ~1.4gb per 4k transcode).
if you are on windows, I believe that it handles video ram differently, so not as much of a problem.
Either way, if you are, or are wanting to get into 4k, I would suggest you read the entire thread @ Plex, 4k, transcoding, and you
