You do not need all that, looky here, what I did. If you can get 2 prong, that is even better.
NO PRONG SET UP(I might be wrong here)
--- run the turn on blue wire from the car receiver (aftermarket) and connect opus' blue wire(ignition wire) to it. So if you are making short trips, do not turn your radio on and the computer will not turn on. however, you can not have your computer on when the key is out of ignition, which makes sense to me

ebcsue I dont need the caputer on if the reciever is off and no sound is coming out.(One thing I am not sure is if the receiver lets out 5v or 12v, I think 5v, it could work...I am doing/testing that next week)
2PRONG SETUP:
---version1: thin wire from battery(+) into FIRST prong, and the blue wire from the opus into second prong. the computer turns on at a flip of a switch whenever, whereever, no key needed. (I dont like this set up, because if you have an after market radio that the computer sound is connected to, then you will here no music)
---version2: The blue (external turn-on)wire from the battery to one prong in the switch, and the blue wire from opus into another. Makes more sence, works only when the radio and the key is in, alogn wiht a flip of a switch. This also allows you to listen to the radio on the receiver, with your carputer on. I like this even MORE!...
Hope this works and makes sense...I will be testing this when I get my car from shop

good luck buddy