@silverhead - Thanks for the information.
@pianoguyy - I was saying it was bad customer service of not contacting me back when they decided to discontinue the HD300, and nothing else. I wanted the HD500 but could not afford it. I have loved using the HD300 ever since I figured out how to get great sound out of it by using a powered speaker, a seven band EQ, and a DI box.
@clay-man - when I bought it they said there would be upgrades of newer amps coming.