Michael,
I have an older Panasonic 616 system. It has been very solid, but it was pre-caller ID and didn't directly support cordless phones. It was great for paging the kids when you didn't know where they were (down-side of a big house). I looked at the Panasonic system that replaced it (a few years ago), but couldn't convince myself to spend that much money. Then one day I went a little crazy in Staples and bought a Siemens 2.4 GHz system. It includes a digital answering machine in the base station, support 2 outside lines and up to 8 cordless phones. You can intercom between any of them. All phones have caller-ID and you can listen to messages on any of the phones. The phones are very small and come with a belt clip and a jack for a head-phone. They have enough range to cover most of my property. My wife has one complaint - she can't page over the speakers like she used too - so can't raise the kid when he's playing the drums. I have one complaint - when dropped on the slate floors, the slate wins. The phones are all still working, but the LCD's are getting flaky. I don't know why, but this was one of the few times I didn't buy an extended warranty.
-david