“KX-TGA641-T compatibility Is the KX-TGA641-T system compatible with the KX-TG6513B system? I want to get a system with 3 phones that is compatible with my old TGA641-T phones. Please include all Panasonic phone series that will work with it. Also, one of my phones will not work on the speaker system is there anything that I can do to fix it? Thank you, Keith”