Yes it can be done.
Front panel audio has two connections for each channel. And in and an out so to speak. One sends the signal up to the jack, the other is a return back to the headers. This way sound is always being sent to both the front panel and the rear jacks at the same time.
I just plug my headphones in all the time and when I want to use them (like at night when gaming and everyone is asleep), I turn my speakers down and put on the headphones.
Pins 5 and 6 are one channel and pins 9 and 10 are the other. I don't remember which is left and which is right (and I really don't want to disassemble my system right now), so you will have to experiment. But for example, if you try 5 and 6 for left channel then you would put Spk Left on 5 and Left Return on 6 and then do the same thing for right on 9 and 10.
Then fire up your system, load up an mp3 in Winamp and put on your headphones. Scroll to the left to make sure you have the channels correct. If they are backwards then just reverse pairs 5&6 with 9&10. If you get no sound at all reverse pins 5 with 6 AND 9 with 10 and test again.
Does all that make sense?