Use:I am building a headless ubuntu serer. It will be mainly used for hosting a minecraft server from home, of about 20-30 people. A secondary purpose will be hosting a samba server. It will be on 24/7, so I would like to use a little power as possible.
16GB will be okay. Agreed, I don't see any 4-slot mini-ITX AMD-based mobos out there. While a SSD will help with performance, I don't see where it would make that huge a difference with a game server.
What will affect the server is your network connection. Are you using DSL or a cable modem for your ISP connection? Also, will this server be on a dedicated IP address or a DMZ off of your home router?
As of now, it will be off of my home router, with AT&T DSL. My internet is pretty fast, I've had about 10 people on a laptop I installed linux on with no problem, aside from the computer itself overheating.