I used to have the a7n8x-Deluxe. I believe the -E has the same soundcard.
Mine had the normal Green/Blue/Pink connectors plus an Orange and Black for rears and the sub. I used a 5.1 computer system so setup was pretty simple. If your case your going to have to experiment with it. Green will be LR, Orange will be Surrounds, Black will be sub/center.
There's a utility on asus' site called "speaker switcher" or something like that. It plays a test tone through the speakers and lets you switch left/right, LS/RS, Center/Sub.
Also the driver has some sound mode presets that will take 2.1 and make it 5.1, if I recall.