2006-2007 Subaru Legacy 6cd Changer Compatability

[sullivanstarship]

I'm looking to get a replacement 6cd changer for a 2006 Legacy, the product number for those is P-203UH (I think the range was 201 - 203). I'm wondering if the unit found in the 2007 models would be compatible, its a P-204UH and has an AUX selection button. Strangely my 2006 has an AUX cable but no AUX selection, so I had wondered if the plug is wired for it even though the unit doesn't have the function installed. I know sometimes there are subtle connector differences that hurt compatibility, so if anyone knows if they can be swapped it would make my day!