Matt doesn't mention in the first post what the white/red wire needs to hook to at all. Take another look at this and your wiring. WUGcatsvt also mentions hooking to a blue wire.
This picture also shows the blue amp turn on wire you are looking for. It's just been cut in half and has a spade connector attached to it. Examine all the wires coming immediately from your deck, and they should be labeled. If you got the RCA cable hooked up correctly to the preamp +/- wires than you should be set once you connect the amp turn on wires.
What adapter are you mentioning? If you were able to get any sound at all through the stereo it's hooked up correctly. The blue amp turn on wire that I mentioned doesn't connect to anything in the above harness, that's why you have to bridge a wire from the other white/red one.