Server size can vary due to how many people play on them. A server that hosts 200+ people has to be fast and reliable but someone who is hosting a MiniLogin Server for themselves doesn't have to have the peaked system requirements. If you are going to run a huge server, I reccomend:

Pentium 4 1GHz
512MB Ram
16MB Video Card

If you don't have these requirements, just run your own MiniLogin server like I do or join one of the servers that are hosted by others.

Hope This Helps!!!

-Wizzel