theres no need to drill a hole, i managed to squeeze 2-gauge cable through the existing grommet (o-gauge was just TOO big)
if the wire youre on about is a thin blue wire then this is the remote wire, this tells the Amp to turn on
The RCA cables also connect to the head unit, but send a signal to the amp to tell it what music it is to play (much thicker, with 2 connectors on each end)