The two different types of input likely have different input levels, let alone a change of avr. OTOH what did you do to setup the sub in the new AVR? What is the trim setting in the new avr for the sub at the sub's 3/4 gain setting? Did you use a y-splitter to use both inputs on the sub?
"I realize that somebody playing free music isn't as commercial as a hamburger stand. But is it because you can eat a hamburger and hold it in your hand and you can't do that with music? Is it too free to control?" - Don Van Vliet (aka Captain Beefheart) discussing commercial success in the music biz