Why not use what you have and avoid any convertor box? And no, more than a cable is required. Figure about 99 to 299 bucks for a decent convertor box.
I have recently bought a new led tv, but it only has one set of rca connectors, and two hdmi ports; I found that there are cables rca to hdmi, but I have my doubts about it since hdmi ports are digitals signals and rca are analog. Will it work just by plug it in? for example the wii console comes with rca plugs, will it work if I hoook it up with this type of cable?