Hi all, Can folks recommend a second display for the Retina iMac? I'll be using for programming, word processing, and illustration. I'd prefer to have a display roughly the same size (27" or so). It won't be the primary display, but used as an ancillary display for keeping open references, programming notes, etc). In particular, do people recommend a 4K display? (Do they run @ 60Hz?) Or, am I better off just getting a 2560X1440 display. If the latter, is there a consensus on a budget alternative to the TBD? (I won't need the built-in speakers or iSight, since it'll be built into the iMac.) Thanks for the suggestions!