I did something in 8 channels about a year ago with Live and M4L. It's kind of a hack but it works. The only way that Live puts out multichannel is through the sends. SO you'll need 8 of them. I don't know what kind of patch you're using, but think of each send as one of the channels in the patch and figure out the best way to control the volume of each send on the track thats playing audio (which can be done using the Live API).