There's another option to upgrade the UHFS,
While you drive the world’s best electric vehicle, you should be listening to the world’s best stereo. BUT here's the deal:
It does not modify the car's wiring, for me this is a big deal. It's plug and play.
I actually have this system installed in my car. (I believe I am one of 2 people on the forums) I LOVE it. I'm thrilled. There's some serious caveats.
Here's a pretty lengthy thread about the system and the lagginess of the development.
Premium Audio System for Tesla Model S by Light Harmonic
They take FOREVER to ship. In fact, they have yet to ship a proper Sub driver to me. (supposed to be within this month) Most people have not received anything.
Even with the stock sub. The system is worth every penny I paid.
If you are in the Socal area, I'd be happy to give you a listen.