I don't know about the Linux setup but at work I have a LinkSys Cable/DSL hooked up to a cable modem and tied into the uplink of a Intel 24-port hub. We are currently running 12 machines off of 1 internet account and have not had any real slowdowns. Also, I use the same router at home with four Win98 machines (4 port router). No problem. Don't listen to your ISP. They will all tell you that story.
Hope this helps.
