Audio Systems: Car Audio, mitsubishi eclipse, amplfiers

Question
My son has a 2000 Mitsubishi Eclipse.  He would like to add an after market amp and speakers to the existing headunit.  I have ran all the wiring except the REM wire.  Most amps will accept the REM to simply come from an accessory connection, I have run several combinations from the fuse box, but I have had no success.  What do you recommend?  

Answer
use this interface it will create the 12 rem out to turn on the amplfiers, when it gets audio from the speakers, if the volume is all the way down it will turn off the amplifier,
this can be install behind the radio or next to the rear speakers

good luck

http://www.oemautosound.com/pc-575-132-pie-2-channel-high-to-low-converter.aspx