All you need for the server is a machine with at least one open port to the outside world (so either no firewall/masquerading or one you can control).
As for the bandwidth, it can use quite a bit depending on the bitrate you're streaming at. At the normal 128kbps rate (around 16kb/s, plus some overhead) it doesn't take many listeners to swamp your average ADSL line.
Oh, and Icecast beats Shoutcast hands down
