The input specs for the Z5500's.
Source Inputs:
Digital optical for DVD or CD players, PlayStation®2, Xbox®**
Digital coaxial for DVD or CD players or PC sound cards (requires coaxial cable, sold separately)
6 channel direct (3 stereo-mini connectors) for 2, 4, or 6 channel PC sound cards OR
6 channel direct (3 stereo-mini connectors) for 3 stereo analog mini audio sources, like CD and DVD players, Playstation 2, Xbox, or 2 channel PC sound cards (somedevices may require stereo mini to dual RCA adapter, sold separately)
Analog stereo-mini (on side panel of control center) for portable CD, MP3,or MiniDisc® players
The optical they talk about is between your source and the amplifier on the speakers, the speakers themselves connect with copper wire to the "amp". This means if you want a smaller setup, it will probably come without the amp that the z5500 come with, meaning no optical.