When my amp shits I whack it on the nose and tell it "bad amp"
Would help to know more about the setup of speaker/sub, how far you are from the speakers and what levels you're talking about particularly. Could be some more power is in order via external amp, and your avr does have a full set of pre-outs if so to accommodate. If those Energy's are accurate with their sensitivity spec, I suspect you are likely into ear bleeding levels, tho