I've never owned Onkyo, but the reason is not because of Sound Quality. I have a lot of respect for Onkyo/Integra for SQ.
Retrospectively, Onkyo AVRs have measured better than most AVRs in their price class, same with Integra vs others. In fact, some of their $400 AVRs have measured better than some $2,000 AVRs.
My only concern with Onkyo is reliability; people tell me they have reliability issues.
If reliability is not an issue, I do not believe Onkyo electronics are bright or forward or anything other than accurate in Direct & Pure Direct modes.
EQ/DSP modes are another matter, and processors will differ here. But in Direct modes, which bypasses all EQs/DSPs, I doubt anyone could tell the difference between Denon, Onkyo, Yamaha, Pioneer, or Harman.