IMac and After Effects CC2017

I'm looking to buy a new computer for professional work with After Effects. I'm leaning towards buying the fastest iMac. Any recommendations on what specifications I need to ad in to the base model? Any problems with working with AE on the iMac: Does it overheat with extensive AE work? Does the graphics card that comes in the iMac support GPU-accelerated effects in AE CC2017?



thanks!

Apple doesn't seem too interested in updating the Mac Pro. I already have three monitors I'm quite happy with, so I'm hesitant to buy a computer with a monitor built in — which significantly hurts the IMac's chances for me. Still, despite updating my video card and such, my mid 2010 8-core Mac Pro is getting pretty long in the tooth.

I've been looking at puget systems.: https://www.pugetsystems.com who actually work with you to build a custom machine based on how you're looking to use it.

Sure, it's PC, but everything I've found online has given them pretty high marks (I've been hemming and hawing about taking the leap for over a year now). I continue to read up on Windows 10 and continue to be torn.

My computer is old- It has served me well for many years. Its an Early 2009, Quad-Core Intel Xeon, 2.66 GHz, with 12 GB of memory, with an Apple Cinema 30 inch HD Display Monitor...