I have the PAC one, that has the Mazda-specific harness. I got this one because I didn't need to splice any wires, and the BOSE speakers have non-standard impedance, so I wasn't sure if it would work.
The description on their site in incorrect, the packaging says that it's for BOSE systems (says non-BOSE on their site). The PAC unit also has gain settings, I did not change them.
https://pac-audio.com/catalog/audio-...cing/aoem-maz2
The folks at mazda3revolution and other forums reported that it works perfectly fine, I followed this guide (see below). The PAC module just plugs into the TAU behind the glove box, and it's before the BOSE amp, so there should not be too much processing going on.
http://mazda3revolution.com/forums/2...plug-play.html