I've been using Panasonic cordless phones for over 10 years. I can assure you that their sound quality is excellent, and I think they are still the best on the market at present. You can get some bases for several handsets, mine came with two. They use rechargeable AAA Ni-MH batteries.
When there is a power outage, they don't operate. I plug the main base into my desk computer's APC battery back-up.