We also purchase System Admin Pro for every single FreePBX install. Part of the initial conversation with the customer determines which other, if any, commercial modules fit their need.
As mentioned above, it is largely dependent on what kind of deployment, but if you are going to do any kind of physical endpoints, I recommend endpoint manager. IT is free with Sangoma phones, but if you are using another, supported phone, this really is a very helpful tool.
I’m always inclined to buy the 25 year starter bundle, I work for and with many school divisions, so we usually use most of the modules in there with Sysadmin Pro, FaxPro, Page Pro and Park Pro used extensively, as it really meets the needs of our education environment, and what our Legacy system offered but better in a VOIP solution. But as others stated, it really depends on your environment.
For a newbie like me, what is in system admin pro that you need? I tried to read about what extra it have and the only thing I found out that was nice was the email server settings bug that’s easily changed in postfix.
So what more tools does it give you, why should I buy it?
I don’t believe the commercial Endpoint Manager is needed if you are doing a virgin install with new phones since you can just buy the phones from Sangoma and the free Endpoint Manager will provision those.