so do you hook up an amp to it is it the same as rca's just as was said above fancy a.ss talk for rcaplugs?pre-amp is generally used in reference to some kind of processor that comes prior to the amplifier.....it takes the rca connection from the HU and processes the signal before it is sent to the amp
now if you were referring to a preout(preamp output) then that is simply the rca connections on the back of you HU that would be used to send the signal to your amp or processor
and your last question vexes me