Aaron,

I went with your "Option 2", and bought the SLU from VAIS Technology last summer. It's expensive, but I got a $100 discount via priuschat group buy. It provides two aux inputs, which appear in the audio system as MD Changer 1 and MD Changer 2 (the Prius audio system has no built-in concept of an Aux input). My empeg output is connected to the Aux 1, and I use the "Disc" button on the stereo to select it. It all works perfectly, and the sound quality is excellent (given the limitations of the Prius JBL system).

As you point out, having the track forward/back buttons on the steering wheel mapped to the empeg, or intercepting the CANbus signals to mute the system during a bluetooth call would be nirvana. I looked into options for the steering wheel controls, but haven't found a product that will work just right. I'm not willing to give up the connection from the track buttons to the main head unit.

I took a bunch of pictures during my install that may be helpful to you, but the whole process was very straightfoward. You will need to carefully trim the dash panel, and it does look terrific behind the smoked flip door. I use a smoke lens, but wish I had a clear one for a little extra brightness in the daylight. I had to dremel off some metal pins in the DIN bracket that are used to hold the existing pocket in place, and I used Charles' suggestion of riveting the empeg cage into the bracket. Getting the alignment right is critical, so take your time. Signal wires are all easily available for power, headlight sense, etc.

If I can answer any questions, don't hesitate to ask.

--Dan.