Have you got a live tester. The stereo wires split up basically into two halves. it's the brown, green, purple, white half (solid and striped) which is the speaker wires and correlates to front right and left and rear right and left. The other half of the wires are earth, constant live and ignition live. I'm trying to remember them all without looking, a live tester is kinda needed, you could link a bulb with some wires to make a tester, then just earth one wire and use the other wire to test for live, if the bulb comes on its a live wire.