Since my OPUS turned on the amp 30 seconds after being powered on, I decided to build a simple 555 timer that would turn on my amp after 12 seconds.
It can be built on a little proto PCB using spare parts (I had everything already in my parts bins), or for around $8 using Radio Shack parts.
Hook up the plus to ACC/RUN/START (that way it doesn't restart when you crank), the negative to ground and the output to your amp's remote line, and viola!
My capacitor (C) and resistor (Ra) values were: 100uF and 100k. Which is about 11 seconds.
http://555-timer.clarkson-uk.com/operation/frames3.html