So I'm intending to buy a 27" iMac soon, and homing in on the configuration to purchase. I thought I had settled on an i5 3.8GHz with the Radeon Pro 580, but I have started to wonder if a lower spec machine with an eGPU might be the way to go. Any thoughts and opinions from the community would be appreciated. Usage with be Lightroom, Photoshop, Web browsing, office apps, and some gaming. I also run a Parallels Windows VM for some work apps, but I am using it less and less. I will probably install Windows 10 in bootcamp to play Age of Empires 4 when it is released. I love, and intend to keep my Philips 40" 4K monitor connected to the new iMac. This requires a display port 1.2 connection to run at 60Hz. A big part of my thinking with going with the 580 originally was that I might need the extra power to comfortably drive the extra 4K display. Would using an eGPU give me more flexibility and performance? I will be getting a BTO with 512GB SSD and adding 16GB of 3rd party RAM with either option. I'm not currently CPU constrained on my Mac Pro with single 6 core X5650, any of the new CPU options will give me double the single core performance, and higher multi core, so I'm not too concerned about the CPU. Cool and quiet is a bigger concern for me than maximum performance.