There is a way to watch 4k videos without having to have 4k. The VLC Lan Player can play 4k with no issue. I know I have played them on my system. I don't remember however if you need to have any changes to the setup of the program.
4k via VLC tested on:
Intel 2600K (no overclock), 8gb, Evga 770 TI FTW2
Yes I agree that 4k is really a large size, so I am selective. If it is a model I really like and there is a choice between 4k, 2k (1440p), 1080, 720, I will go with the 4k only (but the content of the video needs to be good as well, if it is just her doing an interview and no nudity involve then I usually will go down to 720p.). So you just need to choose what sizes are presented here as I have seen many videos listed in various sizes 320, 480, 640, 720, 1080,1440,2160 and 4K (not all but some)