Not sure about the emac. Truthfully, you can probably get on wikipedia or the apple support site and look it up just as easy as I can.
As for a new imac, get a mini dvi to dvi or mini dvi to vga adapter, and you can set it up in seconds. You may have to go into displays under system preferences, and tell your imac where the display is. Mine automatically set it up for spanning, and you may have to tweak resolutions on the displays.
Simplicity itself. My 22" samsung is sitting beside my 20" c2d white imac for 42 inches of desktop real estate.