I dont know which wire it is, but I can tell you how to make your own.
All you need to do is make a 12v switched connection. Just run a 14gauge (around that number) wire from your battery to a switch somewhere accesibly to you. Run that wire from the switch to the amp. Then you have a easy...
First of all, Power Acoustik is junk, so forget them.
Dont listen about MTX being better than Orion. MTX has went downhill in the past few years, and they are relying on publicity of their "Jackhammer" line and tricking ppl who dont know a whole lot about car audio into buying them.
Orion...