I have had Yamaha recievers in the past, the last being a RX1130. Just to let you know, it caught fire TWICE! I then went to a Denon AVR5700 and that was night and day for the better! Also, at the time, I was running 4 Heresys, 2 were Heresy II's. I think the Denon has A lot cleaner power IMO. I don't think the problem is the Heresy/Denon combo.
Dave