Testing results with different configurations:
https://wiki.freeswitch.org/wiki/Real-world_results
Your best bet is to test yourself, no one knows your network (probably not even you) until you put it under stress.
As far as we are concerned, we have FreeSwitch in the cloud with the ability to utilize unlimited resources for volume burst. And of course the cloud has the benefit of being able to scale up with a few clicks if things get crazy. The cloud also has the downside that you have to share resources with others, especially during peak times.
For us storage space is not a huge concern, we have a 40GB SSD drive, the only thing stored on the server are config files and recordings and recordings come right off as they are saved where we move them to Rackspace cloud/file storage.
Hope that helps.