guessing
I cannot say anything definitively-first, because I'm no expert, and second, because I have the Audigy 2ZS, and have no experience with the "Live!" version, but here's how I see it:
With the speaker settings and calibrations in the SB software, adjustments can be made as to "emphasis" per channel. There are no indiviual settings for "volume per channel." All volume adjustments made equally affect ALL speakers.
Also, not being an expert, it would seem that two of the output channels would be roughly identical, except for surround "timing," i.e. front and rear, whereas the third would be different in some way since the "center/sub" would be "static" in terms of surround. I do not know how the output would affect the different channels individually. I do not think that you will be able to individually affect volume/channel.
With the lengths of the cables you are proposing, I also would have no idea how/whether that might change the signal and quality of the output.
Finally, as was stated earlier, I think all you can do is to set the volume/per-pair to the desired level, then use the system volume to adjust all.
Not much help, I know, but that's the way I see it.