Audio Systems: rca wires to stock sterio, dodge ram 1500, stock radio

Question
my girlfriend has a 2006 dodge ram 1500 trying to hook rca wires from aftermarket amp to stock radio got a out-line converter getting sound threw the amp to the subwoofers but volume control doesn't work. i know its sumthin w the internal infinity amp system and i dont no what the right converter that i need is called. i need to know what the converter that i need is called i cant use a simple line-out converter that just taps into rear speaker wires

Answer
Not sure I understand the question but let me try.  You need to feed variable level audio from the head unit to an additional amp and speaker but the head unit does not have outputs or volume control level change. Did I get it right?

Maybe what you need is a hi-lo converter that can tap into the speaker output wires and bring the level down to match the input level of the amp.

You can find such devices at installer.com .

Look here:  http://www.installer.com/main.php?page=hilo

And good luck. If you need more, let me know.