In my experience, servers run into two main issues, bandwidth (good network cards) and video. For the most part, I think any decent processor and RAM would be fine. I think our server is running 16GB of ram, but I doubt it uses hardly any of that. And any processor out in the last 3-4 years would easily keep up.
The tricky part with servers is that they don’t have decent video cards typically, and the server HAS to render the main screen with the current setup of Artemis. So when Ship #1 goes into combat, and the server is trying to render all of the explosions, you’ll see quite a bit of lag. So, the better servers tend to be a desktop computer with a decent video card in them, with lots of available bandwidth.
This is totally anecdotal evidence, so others may very well disagree. This is just what I’ve noticed over the last couple of years.