By the looks of the specs on it, you have optical and digi coax inputs, a couple 6ch analogue inputs (3x mini stereo inputs) and an aux mini stereo input on the side of the control unit.

Not knowing how your PC is connected to it, the easiest way would be to use the PS3's optical connection directly into the Logitech system. This will pass through Dolby Digital and DTS multichannel audio, but not Dolby TrueHD or DTS-HD, neither of which are supported by your system anyway. However, you could input the HD audio tracks using the 6ch analogue connections, tho what I can't remember is if the PS3 has multichannel audio outputs - think you can only output HD audio from the PS3 using HDMI