In a car stereo, you have the ability to place the sound front to back with a simple slider for where you want the sound centered.  I’ve always hated FRONT/CENTER as the only vocal channel available. It’s not immersive. My car is set to deliver sound at the driver’s head as the balance front to back. 

On my Onkyo system, I’ve hooked up a shared channel for the center speaker, so a front center speaker, and a rear center speaker, and I can place the vocal channel front to back at any point in the room just by adjusting the ratio of volume delivered to each center speaker. Usually it’s 20-30% at the back, and 70-80% from the front. It creates an immersive surround sound just on the vocal channel, and it’s far better to listen to then front only vocals. It also means  that the entire volume of a system doesnt need to be played loud, since the goal is clarity, not volume.

I’m using the Arc, SL+, and Sub, and I think this would be a very simple modification that could be implemented to deliver some controllable amount fo vocal to the SL+ speakers, using the app as the front/back voice placement via a simple slider.  The ARC SL+ Sub combo is awesome!