you could always tap into an ignition wire, add a small fuse, and add a SPST switch.....that way when you turn the radio off, just flick the switch off........that is how i have seen most amps wired to a stock radio....

 

 

go under the dash at the ignition harness and tap into the gray/ yellow wire. Its the accessory wire. I have personally never used a relay and have never damaged an amp in my car or customers car

 

Just tap the remote wire into the 12v acc wire going to the stock headunit. Thats what i did. I can't rmemeber what color the wires were but use a test light to find which one it is. There should be two with power, one is constant whether the key is on or off, and the other is only on when the ignition is switched on, use that one.

 

thats what I did too...worked just fine.