" ... I know you guys will have some good ideas for the car audio. ..."
I wish I had your confidence in our ability to help. Being a Mazda owner but mercifully blessed with a non-BOSE system from the factory, I have a very nice audio system in mine. However, those who have the same model but with the factory BOSE system don't report such great success.
I like Mazda vehicles but they have been married to the BOSE car audio systems for a long time (going back to the 1990's). The problem is, for one, it doesn't sound all that great to a discerning ear (but sounds great to the ordinary person) and for two, BOSE uses unconventional interfaces to achieve it's sound system objectives.
For example, although I don't know the exact parameters of your CX9's system, a typical BOSE approach would be to use very low impedance loudspeakers ... 1 ohm is not out of the question. In this way they achieve high power output (a 10w amp into 8 ohms is a 80w amp into 1 ohm, all things being equal)
BOSE is also fond of equalization to compensate for the inherent response of it's chosen drivers. So you often find you cannot simply replace the BOSE system drivers with other, higher quality units, as they are not fed a conventional flat frequency response signal.
The true solution with any integrated BOSE autosound system is to find the flat line level out, if it even exists, at the output of the head unit, and install your choice of power amplifier and loudspeakers. The problem is with the most modern vehicles you cannot always hack the sound system due to massive integration with the rest of the vehicle's electronics.
You would be best served by asking questions in a forum specific to the CX-9. That's where the options available to you will probably reveal themselves. You could then come back here once you are armed with the details of your CX-9's BOSE system, and then, maybe help could be offered. But without specific information to your year vehicle, we probably won't be much help here, as what we may suggest will often simply not work in a BOSE system.