I use a Matrix between my Aurender N100H and my PS Audio DAC. The DDC allows me to feed DSD128 and DSD256 directly to my DAC not that I can really tell the difference.
The 5 volt rail is the weak link with USB because it has the potential to pick up noise from the source. With the Matrix, if you connect an external linear power supply, it isolates the 5 volt rail from the USB source, and in theory should improve the SQ because the LSU is used as the power source.
I've read on other forums where some people have said the external LSU makes no difference and others that have said it made a big difference. It occurred to me that everything is dependent on the noise being generated at the source. For example, the USB out on a PC might be more prone to noise compared to the USB out on the Aurender music server. Does this make sense to anyone? BTW, good topic!