There is a thread over on the AVSForum 'Official Audyssey thread' and lots of info on there including, on the first post, an optimum setup guide:
Official Audyssey thread
You need to make sure that the crossover is turned 'OFF' on your sub, phase to '0' and that the gain is set such that Audyssey sets the amp sub level as close to 0db as you can (+ or - 12db indicates the gain is set to high or low for the setup). I have a 2808 and a BK Monolith (and an XLS200 DF in my conservatory
) and I did find that after doing the full 8 position setup, my bass seemed less boomy, but I got used to it an prefered it. However I discovered thay Audyssey can cause very low end boosting at about 10Hz that has actually damaged my speaker.
Your '200 is sealed so shouldn't be effected by this issue though.