Aurender are great streamers. It is all they do. They are solid investments for the money. I have ushered a Berkeley DAC with my Aurender, fantastic combination.
About the volume control. This is not where you want to control the volume. You want to do it at the preamp / system level.
I have been streaming for over a decade and using Aurrender for more than 4 years. I have two. See my profile.