he's got a sony. i don't know the specific type.
it's a cd-changer (so he has some line ins but only working with the cd-changer and sony has a very special cd-changer cable.)
all speakers are connected directly to the head-unit.

ok, he has a small amp, but that's only a 2channel-amp which is bridged so that he can connect a sub.. but no amp for the other speakers..