But if the player is running at 12v, and the wire supplying it the power is running at 14v, then isn't some of that energy being converted to heat by the voltage regulators?

Or is it like amperage, in that it only draws what it needs?

I admit, I still never understood the difference and relationship between voltage and amperage, no matter how many times I looked at the water-faucet-and-tank metaphor pictures.

And I think once I briefly grasped the concept of torque vs. horsepower, but I think that's now lost again.