Preferably the Dell P2715Q. Will the 27" iMac with the default m9 GPU be able to power a second hidpi screen? Is want to run the Dell at 1440p hidpi. I don't game but I have lots of windows open generally of largely static content (PDFs, sublime text, latex docs, etc). I just don't want lag. Can I get by with the default GPU since I don't game with a second 4K display? Thanks!