Solved! Home theater 5.1

Solution
USB port in an HT box is not standard, either it has it, or it doesn't, you can't ADD to it.

But that's an odd request. Usually people looking for USB port in HT boxes want to pipe high bandwidth uncompressed STEREO signal to it, but you specified 5.1. Modern Five-Point-One are delivered via HDMI (best), Optical (good).
USB port in an HT box is not standard, either it has it, or it doesn't, you can't ADD to it.

But that's an odd request. Usually people looking for USB port in HT boxes want to pipe high bandwidth uncompressed STEREO signal to it, but you specified 5.1. Modern Five-Point-One are delivered via HDMI (best), Optical (good).
 
Solution