You have to have an upload of more then 90 kpbs, anything lower then that and you will notice some quality issues. If i don't do anything on the internet such as download or open up websites i'm good to go, but once i start to do either the conversation goes choppy and doesn't stop until you stop with whatever you are doing. So if you go with something more like 512 download then i dont' think you will really have a problem. i have a 256/128 connection. hope this helps you.
Vonage connection tester, works best with nothing running. 
