Audio Effects on Logitech Z-680

[RMD68]

I currently own the Logitech Z-680 5.1 surround-sound speakers. On the control panel that comes with the system there is a button for effects. The efffects are as follows; STEREO, STEREO x2, DOLBY PL2 MUSIC, and DOLBY PL2 MOVIE. I currently use STEREO x2 because STEREO only does the front speakers. When I was playing around with the control the other day I tried to switch it to the dolby music effect which I thought might enhance my music (these speakers are connected to my computer and I use them primarily for music). When I tried the music setting the audio would only faintly come through the front speakers and with some songs only through the center channel. This was odd because on the STEREO x2 setting all the speakers fire besides the center channel. I am using an optical (TOSlink) connection between my Mac (June 2004 Dual 2.5Ghz G5) in case this makes any difference. Am I missing something or is this just how it is with the Mac stock soundcard? Any help is a appreciated.

Also, if anyone owns this set is there a better way to connect my speakers instead of using the stock wire that comes with it. (Not the commmand center to the computer but the speakers themselves to the amplifier)

 

[RMD68]

Are there any external mods that would allow me to get the true 5.1 surround. I mean anything besides something for professional use. I don't think there is anyway to change the existing PowerMac soundcard it seems to be built in. Is it different on the MacPro's? It's odd the Apple doesn't have better sound options when a big base of their market is Music via iTUNES and also the music production with various software. I can't seem to find anything when I search the net or the Apple Store.