I'm building a home theater PC and I want a set up a 5.1 surround sound channel. I was looking at the Logitech Z506 75 watts RMS 5.1 Surround Sound Speakers, and the biggest speaker had a bunch on inputs and outputs. My question is do I need a sound card as a middle man between my PC and the 5.1 channel or does the big speaker have some sort of integrated encoder?