HCP, here is some terminology in case you're still unclear:
The box that plugs into your wall via a cable wire is the modem. There's really no need for anything fancy here, but owning your own modem is a good idea so you don't pay Comcrap's rental fee.
The box that plugs into your modem and provides wifi is called a router. You can get different types of routers depending on how big your house is.
I think Comcast also offers a combined modem/router device as well.