The board/cpu will have not real issues "supporting" 4k. I think all the newer cards support 4kNvidia 6XX cards
I am almost sure the 7xxx cards from AMD support it as well.
Also, you made at least 2 threads on the same topic, please avoid this in the future. Multiple PostsSometimes
after hitting Submit, the forum may take a bit of time to post the thread, just give it some time and it should do its thing. Repeat clicking leads to multi-posts by mistake.
This is more difficult for all users because you will have users helping you in each thread(makes it harder for you and them to track what has been tried or suggested) and not all in one place.