This all totally depends on what you are rendering and what software you use. The Quadro NVS is designed for powering 8 displays, it won't work well for rendering. If you software supports the 980, it will be better. Of course, if your software supports the 980, I would recommend dropping down to a 970 or bumping up the the 980 ti.
If you need 64GB for your render job, it will be better.
The 3930k and 5930k actually have similar performance, but you will miss out on a lot of features using the x79 platform instead of x99 and you will probably have to spend more for less since the x79 platform is so old now.