Seamz :
If GPU acceleration is a factor with the Adobe Suite it's mostly used for editing and not as much in the rendering. It will be faster with a GPU, but from what I can gather it has to be an nVidia card.
You'd be surprised. I did a couple of tests on my rig and was myself actually quite surprised. I ended up getting a 70% decrease in time with an old AMD card I had lying around and got a 120% decrease using CUDA for the renders in CC2015. YMMV though.
NVIDIA cards are useful for CUDA but Adobe has recently warmed up to AMD and have integrated OpenCL so even if your GPU doesn't have CUDA (and isn't NVIDIA) it will still make use of it and make a large impact on your renders.