Ak, if you're using the M22s with an EP500, they should definitely be set "small" with the crossover probably at 80Hz. If you set them "large"(playing full-range, including all the bass), the sub will usually get nothing when playing CDs, since it would only be sent LFE occasionally present in movies, and of course there is no LFE in CDs. Using a "plus" type of setting, as mentioned by Dr. Horse, adds bass from "large" speakers to the sub, but there's no good reason to use that combination in your situation.
