The key considerations in choosing your supplier are experience and independence. Give extra points to a dealer who has installed several similar systems, but ensure that they are not tied to just one or two manufacturers as this will prevent them from giving a true and unbiased solution to your needs!
Even if your initial needs are limited, buy a system with some possibility for growth – get one with more capacity than you will be using immediately. But do make sure all the phone circuits and line circuits are tested and work at the time the system is first installed; that will save time, expense and heartache later.
Get extra wiring installed
A good benchmark is to ask for at least double the wiring you currently need. While this will add to the cost of installation, it will really only be a fraction of the cost you will face if wires need to be added later.