Consider the following open source software for your small enterprise
Nethserver for ADSL load balancing,
Ntop for network monitoring
Owncloud for private file sharing
Xwiki for Knowledge management
Passbolt for password management
So you have a little growing enterprise and you are facing management problems and need to leverage open source tools to tackle these problems, here are list of open source that could help you out.
Nethserver ( http://www.nethserver.org )
NethServer is based on Centos and is designed for small offices and medium enterprises, It already has many of the open source software packaged and ready to go, among the unique features is its ability to load balance network traffic over multiple WAN connections ( i.e. ADSL) , this way you can have multiple ADSL lines from different providers and distribute the network traffic among them.
Nethserve also provides proxy to cache and accelerate your frequently visited web page and provide shared folders accessible from your private network.
Ntop ( http://ntop.org )
A classic problem where a device in your network clogs the internet connection and you keep wondering which device and what protocol is it using, ntop comes to the rescue, ntop use Deep packet inspection to identify and monitor the traffic and can give you an overview on the bandwidth consumed by each device and in the pro edition, you can block certain protocols or certain websites from being accessed through your network, so you can literally block torrents from clogging your connection. interestingly ntop has an embedded ARM based version.
Owncloud ( https://owncloud.org )
We share lots of private files and you need to have the peace of mind that as an enterprise, you have emergency access if need be to the files and in the same time maintain privacy and file sharing and collaboration among your colleagues. Owncloud is very similar to dropbox but you install its the back end on your own servers and you can install its client on desktops and mobiles.
Xwiki ( http://www.xwiki.org )
As small enterprise, you need to share and keep track of the enterprise knowledge, especially if you are a knowledge focused enterprise, you need to avail your knowledge in a wiki like format and allow future employees to see the old knowledge and avail their knowledge to other, Xwiki comes to the rescue it allows adding Structured content and inline scripting and has extensive User rights management (by wiki / space / page, using groups, etc…) and of course has Full-text search and Version control
Passbolt ( http://www.passbolt.com )
Do you share passwords with your colleagues, Do you track which password shared with who, do you delegate creating accounts with passwords to colleagues and you want them to share it back. Passbolt manages your passwords and through you can control who can view/edit a password, it has browser extension to automatically fill passwords too.