I too wonder if by describing his sub as "overpowering" if perhaps it is just not well tuned.
I know nothing of your sub and it could very well be be perfect but I have heard cheaper subs, especially cheap HT in a box subs, that rattle or sound boomy and end up drawing too much attention to themselves. A good sub should smoothly blend the bass into sound from the other speakers. At high volumes it might rattle the room but you won't get the impression that the rattle is coming from the sub.
Just something to consider. "Does my sub sound fine, I just need to turn it down to match the other speakers" or "does it not sound right when turned up to match the other speakers.?"
