Which computer the best for AE/C4D



I want to buy a new computer, I think to buy one of the best iMac right now (27", i9 3.6ghz, GPU 16GB, 64 Ram)

But I read about users that bought this computer and not happy with his performance in After Effects / C4D.

Also, they told, that cheap Imac will do the same performance in AE.

Which Imac is the best for animation and 3D animation (AE/C4D)?

I want to watch the simulation in AE and export fast.

Also, maybe windows better for AE/C4D in this budget?

Please help, Thanks!