Starting to think about a 27" Retina Imac. I have one external monitor I plan to use with the imac. It is a 32" 2560 x 1440 resolution Benq cad display. I don't do gaming or video. I do some limited rendering (sketchup type work). Primarily it will be autocad work. Is the $250 upgrade to go from a 2gb Gpu to a 4gb Gpu something to worry about? Do it just because you can't upgrade it later? I'm living with a 2010 15" macbook pro now with a massive 256 mb gpu. It gets balky trying to pan and zoom in sketchup. I don't know if thats a software issue, a gpu issue, or a cpu issue. (my mbp has 8gb ram, 1st gen i5, and a 500 gb ssd) What I'm looking at is 27", retina display, i7, 500 gb ssd, 32 gb mem (probably buy with 8, and buy a 32 gb setup from crucial). But I'm pondering about the GPU upgrade. I'm not in a massive hurry, I'll probably wait for the Skylake release, fwiw.