Apple iMac review (2015): 4K is optional, faster hard drives shouldn't be
 

No, it's not just a CPU refresh. Apple started selling a new line of iMacs today, and yes, while they have fresh processors and graphics cards inside, that's really the least of it. Going forward, all the 27-inch models have a 5K screen -- not just...

http://www.engadget.com/2015/10/13/a...-21-5-inch-4k/