How do i set up my Logitech Z906 correctly and other surround related questions.

[Darth-Veger]

For like 4 months long i have my beautiful 5.1 surround sound system connected to my motherboard's audio ports thus creating stereo sound instead of 5.1 (i'm so sorry)
[IMG]http://i.imgur.com/mlS5hm5.png[/IMG]

This is currently how it is set up. As you can tell pretty instantly, the back speakers are pretty far from where i sit. So my first question is.
[B]Should i move my speakers close to me, if so what is the best way to mount them? Since i don't have a wall or something behind me to put them on.
[/B]
For testing i wanted to see how my surround would detect a digital source. So i installed a Dolby Digital+ movie file which definitely supports DD+ but so far nothing happens on the display. (If i am correct, the DECODER light should light up.)
I am using a sound card now which is a 7.1 card but obviously supports 5.1, now i put optical in the speakers and into my sound card but now it only wants to 'run' on 2 speakers.

[IMG]http://puu.sh/1ZmIp[/IMG]
Mind you, this is like a ultra mega to-the-max cheap sound card that costed me 15 euro. No idea if the problem lies here. The card is a Eminemt PCI Soundcard 7.1
[IMG]http://content.hwigroup.net/images/products/xl/113294/eminent_pci_soundcard_71.jpg[/IMG]
I tried several things but when i set the S/PDIG on and select "PCM" its stuck on 2 speakers, setting it on more turns it to a different source.
So, [B]How do i enable the digital signal of my soundcard/surround system for Dolby Digital and such? Do i need a better sound card?[/B]

[loophole]

Have you tried using the analog jacks instead of the optical?