I have been asked to provide insight (because I was given intertel axxess programming and phone system support and maintenance duties a few years ago) to someone going into a new building. Centrex communications will be needed to communicate with other facilities and systems. Any words of wisdom I can pass on to this individual for his selection process of new systems? I have not investigated voip due to the expense of upgrades ie. not needing to fix something that isn't broken. Thanks in advance for any clues.