I've been using an Onkyo Cr515 through MA BZ1's, and I'm happy with the sound quality, but when I plug a pair of heaphones in, it all goes abit wrong. The sound quality is terrible, and no adjustment to the bass and tone levels helps. Would the addition of a heaphone amp cure this, of would it be for the best to step up to something a bit more modern like the Onkyo cs555? I mention the new Onkyo as it has digital inputs which are a requirement for me, as well as the unit being a low power consumer. Your ideas welcomed.