One other thing to try... Most people will setup speakers to be symetrical in a room. i.e. same distance from the back wall and from the side walls. And if your room is symetrical, then you can get a lot of equally timed reflections coming together that can create the nodes. Try moving the both speakers 1 foot off center (both right or both to the left) so they are no longer symetrical to the room. Now your reflections will be misaligned and mistimed and it can scramble the nodes.
I did that with a set of Martin Logan electrostatics where my "best" seating position was right in the middle of a measurable bass node. The shift elimated the bass node.
... just a thought...
- Jeff