Davinci Resolve with fast CPU but Slow GPU Currently I am rocking this setup:
Nvidia GTX 1080
32GB DDR3
SATA SSD

I have the posibillity to switch to a PC with these Specs:
3900x 
R9 290
64GB DDR4 3600
NVMe Gen4 SSD

The main things I do my PC is programming and video editing.
I am unsing Davinci Resolve, which heavily utilizes the GPU AND CPU, would i have a disantvantage using the much older slower GPU but with a much much faster CPU? Or would editing be smoother with the much faster CPU? I am editing mostly 4K:30 footage and redering to 1080p:30 with basic color graiding and effects
From what I've read, Resolve very much depends on your GPU power -- speed and VRAM. I believe there's a preference to turn off at least some GPU usage, but that's probably more of a workaround for something crashing rather than something to be done on a normal basis.
Probably the best place to ask would be the Black Magic forums and over there, Carsten Sellberg answered a similar question with:

In Resolve the CPU is used to run the app, disk I/O and compression and decompression of codecs.
Resolve does all its image processing in the GPU on the graphics card. More CUDA/OpenCL Cores are better.
There are two factors that is important for the Graphics card. The first is, that it have enough vRam to hold a single video frame. For 4K is the absolute min 6 GB of vRam, but min 8 GB of vRam or more are recommended.
The other factor is the CUDA/OpenCL performance. Higher CUDA/OpenCL performance gives a faster Resolve.