Just my opinion and I may be mistaken. Unison is a preamp with arc. My streamer is a dell desktop. From the desktop digital signal goes to dac inside anthem str amp. When using arc I connect anthem to dell desktop digitally. I am not sure however you may have to connect unison between dac and power amp. Then connect unison to your desktop for arc to function.
My music room had echo. Reason walls, floor and ceiling not made of wood. If such a room is empty there will be echo. The more soft furnishing you add to the room such as wall to wall carpet, curtains, sofa, cushions etc the less bright or dull sound will become and echo will not form.
Just my opinion based on experience with anthem str arc. I was disappointed with ARC. Each successive time I ran arc the sound less nice than without arc.
Unison is not expensive specially with the discount. If you do not like arc sound you can sell for minimal loss. Hope you experience success with ARC. Please do let us know your experience with arc.