Need help understanding

So I currently don't understand a certain point in the audio system. I know that in the SR5 you can get the standard 9 Speakers, but I was wondering if its possible to add the extra 3 speakers yourself (after market), to make it 12 speakers? Is that possible or no? And is there any difference between the small infotainment and large infotainment?

 

adding 3 speakers to a stock system isnt going to do anything anyway, either upgrade your system for real with aftermarket in the locations you already have, or just enjoy what you have.

my current system is "only" 8 plus a sub, and it will absolutely destroy the toyota 12 speaker system or anything toyota makes stock really.