Like Newtecky said, most of the cards and phones will migrate to the latest Toshiba systems, and you'd be surprised how much money that saves and how much additional functionality you will achieve with such a minimal investment. I'd strongly consider looking into upgrading and reusing as much of what you have as possible. Then you can start introducing IP phones into the system whenever you're ready. A small investment now will set you up for years of future prof technology.