Just as title states, i didn't have an issue with 4k video playback on my late 2013 rmbp with 16gb hooked up to external 4k monitor but it seems every 4k video i try to play on late 2014 5k iMac which only has 8gb ram buffers or stutters horribly. My internet connection is more than capable at 80mb. Should i bump up to 16gb or will it not make a difference?