I ended up having to use an external modem with the HDtivo and vonage. Many times no matter what settings you use it simply will not work with the internal modem. The newer recievers can use internal analog modems over digital phone lines?For Vonage, you can distribute it throughout the house. Just plug the phone line into a local jack and it spreads it throughout the house. They only thing they recommend is to disconnect the phone wires in the phone box in case they Telco turns the phone line back on. It sends power and could harm the Vonage equipment. So all Directv receivers should work with the Vonage line. You do need to adjust your dial out settings. Check here.
DIRECTV Receiver with TiVo - TiVo Community & Store
Search for Vonage.