they're not giving out the information because it hasn't been released yet - the units won't ship until mid-august - but i called sweetwater, and they said that it will be able to interface with all popular multitrack software - n-track, audition, etc. - and each track AND the stereo outs can be mapped.
multimix firewire 8 = 8 tracks + stereo right and left = 10 total tracks out
multimix firewire 10 = 10 tracks + stereo right and left = 12 total tracks out
multimix firewire 16 = 16 tracks + stereo right and left = 18 total tracks out
i can't wait for some reviews of these ....