Hey Cronkey,
Reason I ask is that for about 450-575 you can simply buy a 2007-2009 Subaru radio assembly. You are right, if you have digital climate controls you CANNOT put in an aftermarket radio system.
However, in 2007 Subaru made the AUX IN standard in the Legacy so all you need to do is order a newer radio.
I'm probably going to go that route soon.
I don't feel like hacking into the radio to put in my own aux-in although it is much cheaper. I would rather have all the controls and ability built right into the deck.
just my thoughts....