Your avr has Audyssey XT which is now the second best Audyssey on an avr (only exceeded now by the XT32 version). XT does have ability to eq the sub, and I'd use it with the avr's setup routine, then, if it sounds bad, then think about doing something else.
What reviews? Link 'em so we can read what you did. Personally never heard that about any particular sub and Audyssey. I heard a Rel once and wasn't impressed but then have no idea what that store did to set it up properly.
That's one expensive 10" sub, though....what makes it worth that kind of money?