I don't know why you wouldn't use the headphone jack in the front, but there is one thing you can do. You can plug a cable with r/l rca jacks on one end to a female headphone plug on the other end. Something like this:
http://www.monoprice.com/products/p...=10218&cs_id=1021815&p_id=5612&seq=1&format=2
This would get you sound...but you wouldn't be able to adjust the volume, because it would be at line level. You would then need something to adjust volume, or a set of headphones with an inline volume control. If it were me, I think I'd just use the headphone jack. But it is certainly possible.