There are three levels of audio system, two of which come to the US. In the US, there is the HiFi system, and there is the Premium Sound system, which carries the "harman/kardon" brand.
We are working on upgrade packages for both. The standard US-spec system is the HiFi system, which has front, rear, underseat woofers, and a center, and an amp. We are looking at upgrading that amp and the front and underseat speakers, and jettisoning the useless center channel.
The amplifier mounts, speaker adapter mounts, and woofer adapter mounts are all off to prototyping! The trunk subwoofer is ready to go to tooling. The wiring is already validated. We know what speakers we will use - we're really close! I'm hoping we have HiFi upgrade Level One and Level Two packages by Thanksgiving and the subwoofer ready by Xmas.