you can also use a 12v+ to trigger your amp to confirm it's operation
then back to what panhandler suggested, see if the sony box is outputting 12v+ to trigger the amp
a lot of truck people here are asking about ipod or mp3 players without a head unit
so when you get everything figured out, post up a build and review in this forum
just to be clear... no speaker hookup to the sony unit
rca cables to the amp and all speaker/sub hookups to the amp
is how you hook that up
crutchfield.com/Manual/158XDPM110