orange = digital out / blue = line in / pink = mic jack / green = front out / black = rear out. plug phones into green,in surroundsound mixer select headphones, if speakers are still active turn sound down by the independent volume control then use the volume control on the taskbar for headphones.
Not using splitters myself,as I only need to do this now and again. maybe someone on here has tried it.Having looked at those speakers I would think they should be connected to your sound card on their own for quality.
i do it like this. i have a double jack plug in the main line out socket of the audigy sound card and an short audio lead to the front of my table. i can plug in and out the head phones when evr i like. by turning the remote control to the speakers off i can have just the head phones on.
i have an ordinary sanyo set of phones purchased from a car boot.