Z-5500 and digital audio questions

Hi everyone I've recently bought the Logitech Z-5500s as an upgrade from my X-210s and although the sound is miles ahead of my old speakers there is still a bit of noise when it's supposed to be silent. I've got it on the 6 channel direct connection to my Sound Blaster Audigy SE 7.1 card and was about to buy one of these:
http://www.pccasegear.com/index.ph [...] s_id=7063&
one of these:
http://www.pccasegear.com/index.ph [...] s_id=6091&
or one of these:
http://www.pccasegear.com/index.ph [...] s_id=6861&
However all I really want is good sound from music and DTS from movies. EAX is bottom of the priority list and I've heard it doens't really work in Vista.

Anyway I was wondering if I could save money by either connecting a coaxial cord from my motherboard (Gigabyte P35-DS3L) to the control panel or buying one of these:
http://umart.com.au/pro/products_l [...] &sid=20886
and just connecting that to my card or would these methods not do my speakers justice?

Also I've got some spare speakers ( http://www.gale.co.uk/goldmonitors.html) lying around and was wondering if I could just swap out the front left and right speakers for them without any negative effects (like blowing the speakers or something) it says in the manual not to but I can't think of a reason why you shouldn't be able to.

Thanks in advance