just look at the amp as being multiple amps in one convenient package.
i can't seem to find a decent pic of the input/output side, but found the specs..
the problem with many computers is that setting up the audio to work as 2.1/5.1 is that many computers will then start looking for media that has a *.1 audio track, where your normal audio file will only be 2.0 type-- meaning there isn't gonna be one..
there are certain boards, and audio driver programs that have ways around this, but generically speaking, most boards don't..
the best option is do similar to the faq method-- run a single pair(both the left, and right channels) of rca cable from the carpc to the amp, then split it to both the front and rear channels, and set the 5th channel to use the signal from ch 3+4..
from there, use the onboard crossovers, and gain controls to setup the sound.
the disadvantage of course though is that you loose your fade controls--currently, i have not seen any carpc-related program that allows you to have a fader control..
some have been able to use the volume controls for the outputs of their sound card like a fader, but that is about it..