That's funny... my wife and I have been looking for a new vehicle for the last couple of weeks and I'm asking everyone if the aux in is standard.
Yea, you're not the only audio nut out there. The Hyundai actually had both the aux in and a usb port, a much better solution, but I got a better price on the Matrix, it gives a much smoother ride, and there were some other features like fold flat seats that really fold flat that I really liked.
Jay, that was my impression of the bass in a Sienna (comapny vehicle) I recently drove. I bet I am looking for a woofer solution to replace the sloppy bass before the year is out.