@BoredSysAdmin: I think what disasterpiece has been doing is downmixing to stereo and then let his Z-5500 upmix using DPL2.
This creates fake surround, because almost all spatial information will have been lost. As soon as the downmixing is done, all the sound info will be flattened into two channels. The system can no longer tell whether a certain part of for example the right channel used to be part of the front right, the surround right, the center of the .1 (LFE/subwoofer). All DPL2 does is guess a bit and put some reverb echo of the front channels on the surround channels. This result is not very impressive. You can no longer tell whether a sound is coming from behind you of from ahead of you.
What I would do, concretely, is this: try and get a refund and/or sell your sound card, get a receiver with 5 speakers and a powered sub and connect your PC via hdmi to the receiver. Your GTX 670 no doubt has hdmi output and to make it very simple: hdmi trumps all. Like with optical you have digital signal, but like with analogue you can also send discrete surround signals over the cable, meaning you no longer have fake surround or need ugly hacks like DD Live. Not to mention that hdmi also carries video, so you only need to have one cable rather than two.
To make a long story short: don't bother with optical, sound cards or analogue anymore. Get a receiver, go all-out hdmi and let the receiver do all the work. This makes sound cards obsolete. Creative is NOT happy, which makes me very happy
, but that's beside the point.