In general, the bass requirement for movies is actually more demanding in very low frequency reproduction (i.e. less than 30 Hz) than music. This is the range where a lot of movie special effects occur. If you are in an appartment or condo, you may not want a subwoofer that goes much below 30 Hz because of potential complaints from neighbors that the sound is traveling through the walls to loud (actually too deep). If so you can get by with a relatively less expensive subwoofer, because you pay more of a premium for less than 30 Hz bass.
I would try and find reviews of your subwoofer candidates and see if you can eliminate some based on published performance and critical listener reviews. Then maybe you could go and listen to a few that are still candidates. It is hard to compare subwoofers in a store because so many factors with room interaction are involved. If you do find a subwoofer that sounds good in a store, at least you know under that room's particular acoustics the subwoofer has the potential to sound good. Parametric equalizers (i.e. RABOS, BFD, Audyssey in receivers, etc.) can be used to partially compensate for room frequency response problems. Audyssey (in receivers generally) also does correction in the time domain which provides a very clear and directional soundstage in typical house rooms. There are also room acoustic treatments which can be used to get rid of room acoustic problems. You can read about them in the room acoustics forum.
