since u heared the pop sound or " A Dub sound " in the speakers that means that the rear amp is OK ... first u need to make sure that the signal from the line out is audiable u can use an ear phone or a high impeadance headphones ( 600 Ohms ) to hear it. once u made sure its there. u go to the next point of attaching it to the plug. until now I don't know what u have on ur dash. but I was looking at the first post with the picture in, it shows all the connections needed but nothing related to the speaker Input to the rear OEM amp. that's the major problem here.

you should have 6 wires ... left common and right common LR front and LR rear. if u dont have those wires u will not be able to feed the OEM amplifire.

if u cant really find them ... add me on ur msn and I would help u up...