Yes, sounds to me like you are over working the sub also. I agree with positioning too. A REL is not like a typical subwoofer, so forget about what you've been told or learned about subwoofers, and go read this link at the REL website.
(Actually print it out).
http://www.rel.net/setup.shtml
(Actually print it out).
http://www.rel.net/setup.shtml