Please note that there are now two kinds of GPU acceleration in Ae itself. This first is the ray-tracing renderer, introduced in CS6, which uses specific CUDA-enabled cards for accelerated rendering. This is now obsolete, and I'd advise against basing your consideration around its needs. Ae CC 2017 has introduced a new Cinema 4D-driven 3D composition renderer; you should consider this the replacement for the old ray-tracing renderer. The new C4D renderer is CPU-based, but it's substantially faster than the old ray-tracing renderer in CPU mode.
There are also the new GPU-accelerated native effects. (This is a completely different architecture than ray-tracing render GPU acceleration in CS6.) This is limited to handful of effects for now (Gaussian Blur, Lumetri Color and Sharpen in Ae CC 2015.3 and Brightness and Contrast, Find Edges, Hue/Saturation, Mosaic, Glow, Tint, and Invert in Ae CC 2017). This uses CUDA or OpenCL on Windows, and Metal or OpenCL on Mac. I haven't seen any specific guidance from Adobe on cards for this new architecture, so I'd probably default to Premiere's list of supported GPUs as a good baseline.
Of course, some effects like Video Copilot's Element 3D or BorisFX/GenArts Sapphire may still have their own GPU requirements or support, separate from the general system requirements of After Effects.