Upgrading my PPro System... Advice needed, please

Hi... I've got a three year old PPro editing system (windows) that I'm thinking of upgrading.  Of course, using the latest versions of Adobe CC 2017

Currently using a intel 3770K (4-core) with 32GB RAM and an NVidia GTX960 with 4GB RAM.

I've been hired for more and more 4K stuff and now shoot everything in 4K with a Sony a7S-II at 100Mbps.   With all respect, I'm not looking for a discussion of buying an external recorder for Pro-Res or using Cineform or anything like that.  I need to take stuff directly out of the camera and edit it. 

In addition, I've purchased a Phantom 4 Pro that is able to use h.265 at 100Mbps and I want to use that, in-transcoded.

About 50% of the time, the 4K coming out of my a7S-II plays great, but I get a lot of stuttering, which is usually solved for a short amount of time by stopping playback, waiting for a few seconds and starting again.   But as we all know, that interrupts the creative flow and usually ticks off clients!

I am considering the following:

Intel i7-6950X (10 core) with either 32GB or 64GB RAM with an Nvidia 1080 with 8GB RAM.   I am not opposed to using AMD video cards with Open-CL, but I do a LOT of transcoding with apps that use CUDA and I don't want to buy a video card that only really works well with Premiere and nothing else.

I, honestly, haven't really been too unhappy with final encode times (either 4K->4K or 4K->1080p) -- what I'm really looking for is smooth playback of the timeline.  I understand, that short of scaling, Lumetri Color and GPU effects, the CPU is used mostly for decoding for timeline playback.  Correct?

Also.... looked at Adobe's "official" Video card list--- why do most of the ones they list all seem like they're older models?  Where's the newer graphic cards?

I'd really appreciate some advice on the proposed system.