I have the same APC 15, but it’s in my living room system which is a 5.1 for television and movies. Have never tried in a 2-channel system. With this said, and from my recollection, this particular unit was made for media/HT systems. Long ago I tried many power conditioners and this was the only one that simply protected and didn’t kill dynamics.
Couldn’t hurt taking it outside of the equation to see what happens, though.
Couldn’t hurt taking it outside of the equation to see what happens, though.