[TIPS] Hardware sizing guidlines

I am looking to replace my POS Samsung 400dsi PBX with an asterisk server

I haven’t yet been able to find any information regarding Hardware Sizing. I would like to be able to scale up to 20 users internally (on the LAN) and 10 remote users. What size server should I be looking at? I have lots of additional questions about CPU, SMB, RAM, etc. But I am hoping there is some unrealized resource out there that someone can point me to.

I have read through some docs and intend to follow the ‘less is more’ methodology in configuring the main server. I will set up an additional server for the web/mysql features. However I haven’t found any documentation outlining this kind of multi server setup. Is there any?