the answer is....there is no way to switch. The speakers will play both inputs if you have both inputs outputting sound. I can have music playing from my PC and play my 360 and the speakers play both sounds. If you only want to hear one input at a time, just make sure there is nothing being output by the other input. Otherwise it will overlap.
That's the same question I have. I own the Logitech z-2300s and am very pleased with the sound. I am using a Samsung LCD TV for PC monitor and TV in the bedroom. The old z-2300s have inputs for the PC but no RCA inputs to connect to the Audio out from the TV. I noticed the Logitech z-623 have both RCA and PC inputs. How can you switch between the two? I can have Pandora playing on PC and a TV show going and don't know how the speaker would discriminate between the two without a switch.