Also, remember consider that different DVDs (movies) will play at different levels. Typically, older films will have a less LFE response. Some newer ones might be over done. Remember also to check how your receiver responds to how you set your speaker settings - large or small. Sometimes, as with Denon once you set our center to large it almost completly shuts down our sub - unless your sharring the lower frequencies between the two. Even if your reciever doesn't shut off the L.F.E. channel it might cut it back a bit.
Also, some sub require a "Y" cable to split the signal input coming from the receiver.