Hello everybody

I'm looking some refurbished workstations to replace the previous one that died due to a storm.
I've 5 FullHD Panasonic PTZ cameras that are H.264 inputs currently but I'm planning to move to NDI, 2 SDI inputs on a Blackmagic pci-express card, 1 broadcast audio input USB card and I use some videos to play as opening and closing of the streaming. I stream to 2 different destinations with different qualities. The workflow is simply a streaming that I open/close with a video and switch the cameras.
What minimum configuration do you recommend? I'm looking for refurbished workstations so keep in mind that maybe I won't find 5000 series NVIDIA cards but older series, same with the CPU.

Thank you