hmm.. i dont know much about those diagrams questions.. but, the thing i did for the loud anoying pop sound when the pc were booting, were just to have the 12V from the OPUS, connected to the remotes of the AMPS, no more poping sound, cuz the amps are a bit slower than the PC. The only downside, is that the music keeps playing for 5 sec after the car is switched of..
the transistor thingy, the BASE .. i think, is allways the pin in the middle, was it a NPN transistor? .. if so, i dont think it would matter either way you but it.. dont know for sure tho..
good luck meastro, or all the other electronic guru's are sure to help you in a while