Wow, sounds like nothing has changed then in regards to receivers. I could be wrong, but I don't think it is Audyssey that is setting the distances, just like large/small. I believe it is the receiver, but I could be wrong.
All I can say Adrian, is that my EP600 Digital based Axiom sub is about 12-13ft away from the primary seat. My Denon had it set to 26.6 ft. Changing mine to 13ft was like night/day, so much better.