I've been thinking of getting an external display or 2 for my MacBook Pro Retina late,2013. It has the discrete GPU (2GB ram) & Core i7 w/ 16Gb of RAM. I'd like to get 2 displays, I'm thinking Dell 24" or 27" 4K displays running them at full resolution and still using the MacBook as a display that just has Outlook or Tweetdeck or something like that. It seems like you only need one DisplayPort to power one 4K monitor and I can use HDMI to power the other and keep that 2nd ThunderBolt Free for other tasks. My concern is will I see any flickering of windows, slowness? Time between switching full-screen apps, etc? Anyone running 4K setups and having issues?