Make your own media box?

Archived from groups: alt.tv.tech.hdtv (More info?)

I've noted that several of the higher end plasma TV units come with
media units that take all the connections then use a single or dual line to
connect to the TV. Is this something you can do on your own if you like a
plasma that doesn't have a media center? Do "switcher" boxes that would
hook up to, say, the Plasma's DVI or HDMI ports, and take the signals from
you DVD player, tuner (or has a tuner), etc. just like one of those media
boxes?