2 radio connector ports - which is used?

Thanks for all of the tips from the USA and Canada regarding changing my CD
player out. I have learned that the 2004 harness for connecting the
CD/Radio/Cassette players is different from the 2000-2003. Ha, ha - I called
Staurn to tell them that I was looking for the other connector and the reply
I got was that they were different. That much I already knew. He was still
unable to find the piece I wanted in his catalogue, so I went online...
Found an aftermarket harness that has the correct 24 pin connector at the
end, but didn't find a 12 pin connector to fit it.

So here's the question...

On the back of the unit I am going to install there are 2 different ports to
connect. A 24 pin and a 12 pin. Does anyone know if this unit (Part No
22684454 - 6 CD Changer / Cassette - from a 2003 Ion) was connected via the
24 pin blue connector or was it connected via the 12 pin white connector -
or does it matter? (Or are they BOTH supposed to be connected somehow?!)

I am in the process of obtaining the 24 pin blue connector / harness, but
will I still need the smaller harness that bridges between the blue Molex
plug to a white 12 pin? (The base model that I removed from my car had only
a 12 pin connector on the back - not the 24 pin, and it too is different
from the model I wish to install.) I know there is a solution, because
anything is possible. I just want to do as little splicing as possible.

Thanks folks!

Warren