The SoundTouch Controller has been discontinued. Much like AirPlay, these controllers will not be compatible to connect with the newest series of products, but will remain supported for all previous generations of SoundTouch hardware.
This does mean that the the Series II home theater adapters would not work with any extra SoundTouch Controllers you had connected as an accessory for the original adapters. You should absolutely consider this factor before changing that hardware out.
As we described to you in a different post, using a single Series III speaker for Bluetooth connection (Such as the ST 20II you have now) would allow you to rebroadcast that signal to some or all of your existing products as-is. There is no large benefit to replacing those Home Theater adapters in this setup. Doing so would simply create multiple redundant Bluetooth inputs for the house.
Hope this clarifies. Thank you.
Sep 15, 2015
We can definitely understand your frustration and we are glad for the feedback. Our product engineers do read this forum to understand what our users are saying. While they don't provide any direct response, it is still good that you express yourself here.
To another point: On most mobile phone you should be able to silence the notification/alert noises separately from adjusting the volume on your music. These settings should allow you to enjoy uninterrupted music while using the Bluetooth rebroadcast feature.