go on youtube, they have like 10 pages of 4k vids..not movies as there isn't movies released in 4k yet... the closest you can come to is download a Blu-ray movie in MKV format but those are HUGE! like 30GB but I'm sure would look gorgeous on the SP3
Surely your better off watching 2k movies on the sp3 as it has a 2k screen. 4k seems a bit of a waste on a 2k screen or am I missing something?