There was a post on AVS about three weeks ago about the same "issue".
Poster didn't know that sub volume is set on the remote. They thought theirs was bad also.
The volume knob on the back is weird...it just spins and spins.
Best to never touch it.
As far as trading his Pioneer for a Denon due to "need more settings", our poster probably doesn't know that most of the good stuff/settings on Pioneer/Onkyo/Integra are on the web interface.