What to buy to get faster rendering time?

If I want to buy a computer that will be exclusively for running:
DAZStudio (Iray!)
Poser
Various 3d Modeling software
Video editing software like Sony Vegas
... for the purpose on getting the fastest rendering time and workflow with little lag or delay. What computer specs should I be focusing more power on?
Comments
Which version of Poser? Iray will use an nVidia graphics card, as long as the scene fits into its memory (so how complex your scenes tend to be is a factor), Poser 11 has a GPU-accelerated renderer but older versions use only the CPU. I don't know if Sony Vegas will use the GPU, if not (and if you typically have to wait for it) then you want a faster CPU than you do otherwise. Much the same applies to the modellers - do you often end up waiting for them, or finding them laggy in use, and do they take advantage of GPU acceleration?
Vegas does use the GPU in part for rendering.
From Magix website (they own Sony Vegas now) "The MainConcept AVC/AAC encoder has been replaced with the MAGIX AVC/AAC encoder, which inherits the same functionality and adds rendering acceleration via QSV or NVIDIA NVENC (supported NVIDIA GPUs). QSV is now an option for GPU acceleration of video processing."
https://www.vegascreativesoftware.info/us/forum/faq-graphics-cards-gpu-acceleration-for-vegas-pro--104614/