Looking forward to your results! Ive been wanting to do the same thing.
I hope this method works better for you than the method my install shop used for me! I think the biggest difference is that I wanted to add an amp to the front/rear speakers also, not just bass. That is where the amplified chimes comes from I assume? Long story short it was a pain in the neck and I had to separate the two systems which sucks in a few ways. Good Luck🤞Yes I hear of people disconnecting the Bluetooth mic over the head rest because of the chimes. So this custom harness I’m getting works with the factory Bose unit. It’s all plug and play so I don’t have to void any warranty. I can add a sub and amp. And also it takes care of the chimes that people with their blazer are having problems with. If you want I formation on the website it’s LLJ customs.com also look them up on YouTube they have one on a 2019 blazer.