First and formost, the PC 360 is native stereo out only, though since surround 5.1 is a gimmick anyway...Easiest thing to do is enable Dolby Virtual Surround to simulate 5.1, since it does a better job then "real" 5.1 on headsets.
I'm going based on my version of the S/W for the Xense, though I imagine the settings should be about the same:
1: Set "Audio Channel" to 6/8 channel. This tells the S/W to expect to playback surround sources.
2: Set "Analog Out" to 2 Speakers. This tells the S/W to use the standard analog output port (which in this case, the PC 360's are connected to).
3: Enable Dolby Virtual Speaker (And 7.1 Virtual Speaker Shifter, if it suits you). This enables the Dolby Virtual Speaker to simulate 5.1/7.1 on the stereo output port.