it'll have everything you need to plug em into the computer, and its got its own amp like all other speakers so it runs off a power point and no it doesnt use power from the computer - theres no where near enough juice from a sound card to power speakers, earphones at best.
The Z-5500 draw power from the usual AC outlet. Power supply is built in with external heatsinks and so you have just a cord.
Due to the high power draw, if let say your heating/ AC unit in the basement goes on/ off randomly, you might hear a static interference from the speakers or sub makes a poof sound. I know mine does that since my room is directly above the unit.
THe 3 color cables is for the main, rear, and center sound inputs.