If you are only looking for back-and-forth communication and not music and such, the easiest solution would be to use your phone system. Several friends of mine with larger homes find that to be pretty effective since most rooms are going to have a phone anyway. You can also use this same system to control gates or your front door locks. Someone pages from the driveway and you key in a code and they're in. No reason to set up a bunch of separate systems when it can be all in one package.