I'm thinking about getting a pair of the Lightspeed 15XLc headset. For those familiar with this model, I have a question about the aux input. I presume it's a stereo input, but what sort of signal level does it expect? Can I connect the "headphone-out" of my walkman to the aux input of the headset, to play music? Or does it expect a line-level signal? Personal music devices (CD players) often have a headphone-out, and not a line-level output.