I can't decide whether I should return my 15" maxed model and swap it out for a 13" ntb and eventually get an updated iMac when they get released or keep my 15" and run dual external monitors. Ive never run a laptop in clamshell mode before or even hooked it up to an external. How do they run ? does the fan kick on? I always had desktops so making my laptop a desktop replacement would be new to me. To those of you who have how do you like it? do the fans constantly kick on? I plan on running dual 32" 4k monitors. Any issues with performance ?