As a backup witness, you don't need to worry about high performance server yet. I can see for example that you have 128GB of RAM, that's not necessary. The recent version of hived does not need that much memory for a witness node. My server only have 32GB. And you also have 2x 3.84TB which is way more than the current disk usage of around 630GB. You should be able to find a working server for 50-60 USD. You could even drop the memory down to 8 - 16GB and use more disk for the state file by sacrificing replay time.