I've always thought of taking the pludge...
Though so many ISP have an upload cap. I'm curious how long you have.. a local ISP "Novus" ( offers 10mb wan link ) However the have a bi-directional cap.
Since Vonage create a constant stream of packets.. that would munch on the monthly limit..
Do you have a calculation of how much bandwidth is used for this application? ( a 15KB/s stream? )