P5LD2 Deluxe's ALC882 audio jacks.

I have a 5.1 speaker set and using onboard sound currently. Planning to get a Xifi later. Good idea? Ok. Here's the problem. Ive updated to latest drivers from Realtek's site. The problem is the audio jacks. Since I'm using 5.1 the rear speakers are consider Rear Speakers and should be plugged into Rear out right? I plugged it in to Rear Out but there is no sound from the rear speakers if I choose 6 channels. Only 8 channels works. The solution is by plugging to Side channel because Realtek's 6 channels have only front,sub and side, no rear. Is it a bug or I should plug it to the side speakers's port? Please advice and thanks.