I'm not familiar with the '15's so not sure if you'll lose any functionality. The amp is nice but as far as trying to add more power to the stock sub...probably already driven hard as it will take. That's part of the reason Bose uses 2 ohm speakers- they don't need a ton of power. On my '02 Denali, I removed the OnStar (didn't work anyway), upgraded to a DD Sony HU with a PAC steering wheel control converter and didn't lose any functionality. Chimes still work, etc. Added a bu camera, replaced a blown Bose speaker and replaced the Bose sub with a 10"JL in a Thundermax enclosure in the rear side panel powered by a good amp. All stealth and an awesome hybrid system. Any reason you're replacing the Bose door speakers? Might do the HU first. Mine really woke up the speakers, then I just needed more bass.