2003 Chevy Stock Deck w/ system

I have recently purchased a 2003 GMC Z71 and am ready to install a system.  I want to use my stock deck so I can keep my door chime and steering wheel controls, + it came with XM and I don't want to change that.  I have heard that I need some kind of relay so that my amp will be powered when the engine is not on.  I hear that the engine must be on for the amps to get power, don't really understand that but thats what i've heard.  I purchased the speaker wire to RCA kit and know where to splice my remote wire.  Can any of you help me with this, have you had the same problems.  I have a line of new trucks waiting for an install and I can't do it.  HELP!!!!!!!!!!Seth Johnson

You do not need any kind of a relay to turn on the amps when the engine is off. However your truck dose have a class 2 data bus system http://www.velocitymotorsport.com/install_notes/OBDII.htm. The main thing when installing aftermarket amps is that there is no switched 12 volt or remote wire to turn on and off your aftermarket amps. You will need to tap into a switched ignition source for your remote wire. Other than that it’s a simple install. Just hook up your high to low converters after your factory amp and tap into a switched 12 volt and your good to go.