Grab, in terms of connection speeds, the worst case I know of is Jeri who has a 56K modem but can only get a 28.8K connection with her ISP and she sounds great.There are more issues than a simple connection speed though, others with seemingly faster connection speeds seem to come through worse and I can only guess that this is due to a particular internet route and web traffic (MMario will know more about traffic than me).
Try it and see what happens.
Jon