I have the metrum acoustics onyx which I had upgraded with the DAC 3 chips. Cees who is the designer of both the Onyx and Morpheus mentioned that with the DAC 3 chips the Onyx is essentially equivalent to the Morpheus as they both now have 16 DAC chips and their design is very similar.
I also have the Metrum acoustics ambre streamer which I highly recommend as it is very well built with upgraded clocks, linear power supply, etc. and has all the digital outputs. In my system USB was the worst sounding and the images and vocals were thinned out. I2S was the best connection between the two and images and vocals definitely became fuller and the sound more transparent and dynamic. It's possible the Morpheus has a better USB input than the Onyx but I would think the other digital inputs on the Morpheus, especially I2S will be better.