I've done some checking around and it appears the "bigger, better" Pioneers and such do not support AUX inputs at all. I'm using an (ancient) Realistic at the moment to switch between my head unit and Carputer, only because I couldn't find what I needed. (Well, and old junk is cheap and easy to use when you want the carputer working NOW) =D
Any suggestions on a passive EQ?
The current system is working great, but I need to stop hiding that old eq in the center console and get it out where it can be seen!

Additional thought: Does anyone know of a unit to switch between RCA inputs? Maybe my solution is a cheap switch into a decent EQ? - Googling now...