I am not sure why your system seems to act differently for music vice other audio sources but the equipment should sound the same based on system and equipment response. It could be that the response of the sub is better suited for movies than Music. Or it could be that the room is affecting the sub right around the crossover point such that you hear it more with music. Velodyne used to make the SMS-1 digital subwoofer management. Outlaw sold them for a awhile, but they are no longer. It would give you precise control of the crossover from 15 to 199 hz in 1 hz steps. It also allows you to adjust the slope in 6db increments from 6-48 db. It also analyzes your setup and displays a curve to allow you to make your choices easier.

http://hometheaterhifi.com/volume_12_4/velodyne-sms1-digital-drive-sub-manager-12-2005-part-5.html