I just acquired a 2012 CTS Coupe with the navigation/Bose speaker setup. While decent for a factory stereo, I want to upgrade the stereo to audiophile standards to make full use of the super-quiet cabin. The challenge is I cannot find anywhere on the Internet what size speakers are used in the factory speaker locations. I see speaker grills on the dash (one by each roof pillar + one center channel speaker) + speakers in the back panel (possibly two more speakers + a subwoofer?).

Hopeful someone has gone through this process and can tell me what size speakers are used in these locations.

My plan is to use the factory head unit and then use a JL Audio Cleansweep to bypass the Bose circuitry, then replace the dash/door speakers with upgraded equipment (probably Hertz) and a different subwoofer that can reach lower frequencies than the stock driver).