Which CPU for Cycles?

Hi, i want to render with Cycles. I will buy two 1080ti or two Vega 64. Which CPU would be the optimum?
Is a higher-clocked CPU with less cores better or a CPU with more cores? Frequency or core-counts for rendering in Cycles?

So you plan to render using GPU mainly?
Does CPU decision depend on any budget that you can spend?

Yes, i want to render with GPU only.
Budget for CPU and Mainboard: max = 1000.- Dollars … could get a used intel 5960X for a good price. But maybe a CPU with higher frequency is better if i want to render with GPU?

Cycles uses one CPU thread at 100% per GPU. So if you plan to render with GPU, it is not worth spending on expensive CPU like 5960X. Just buy an i7 with good single thread performance to privilege performance within blender:

if you are not in a hurry, you may want to wait for new Intel processors to be released soon.

Thanks a lot for your answer!!!