Fast internet connections behind your actual VoIP network doesn't necessarily mean fast and smooth VoIP capabilities for you and your colleagues. Certain devices involved in a VoIP service are required to be as efficient as possible. Thus, I think you should make it a point to collar the most knowledgeable techie you know on VoIP networking and squeeze the information you need out of this person by all means necessary! Off with him and his head if you get everything from him, 'cause he'd be asking for some sort of compensation, I guess. Anyway, this would be a desparate measure for you to make if you have an equally desparate looking bankbook!
With that out of the way, let's start on the
VoIP phones that you plan to use with your actual VoIP network. This is the aspect of an actual VoIP network which hackers love the most. You see, a VoIP network that has been secured on its network configuration settings would still have to be properly configured in the settings of each VoIP phone within the entire network. A non-tweaked VoIP phone configuration setting would result in an easy backdoor for hackers and eavesdroppers to enter. With this all said, I think you should do what you have to in securing those VoIP phones you plan on using with your VoIP network capabilities. I think this isn't just a tip for those VoIP enthusiasts, but for those newbie VoIP pranks and hackers as well!