Just received my iMac this morning, was just about to test a 4K through Plex to Xbox One S, and to my surprise, it seems to be pushing this Mac to the limit. CPUs all hit 95% to 100%, and every 20 seconds or so the movie stutters. Both the iMac and the Xbox are hard wired via ethernet, as far as I can tell, the Plex settings are maxed. Any ideas? I can't justify the 3K I spent on this and can't even stream my 4K movies through Plex. i5 3.4Ghz, 24GB's RAM, 512SSD.