I had a ground loop problem with connecting my computer to my 2150 using the USB port. I had been troubleshooting with Steve at Outlaw on and off for a few weeks. After much trial and error, connecting and reconnecting, I narrowed it down to the audio output of my satellite receiver which I use to listen to Sirius from Dish . A Ground Loop Isolator (Scosche brand)from Wally World solved it .
I know some others have had ground loop problems with their usb , so if you do, the tech guys at Outlaw are more than willing to help.

Now that I've got it solved , and listening to music connected via usb more, I really can't tell any difference between this and my regular CD player playing discs on my computer or using wav(uncompressed) files. While I'm particular about sound quality to a point, I'm no audio perfectionist , (if I was I'd be in an asylum because I'd be chasing what doesn't exist in my world) .... so your results can and will vary.

The bottom line is the USB input is a completely viable option to use. I wasn't sure at first, listening to compressed files, but uncompressed ones and CD's sound as good as they were intended to be.