Better to just turn up the center channel volume by 2-3 db, for movies that have softer sounding dialogues if one is running a HT setup with a ctr. channel.Most people bump up the volume to be able to hear soft spoken dialogues properly while watching movies, including me as I live beside a highway. But a better solution would be to block sounds by closing doors and windows, reducing fan speed and may be even putting some sound boards to reduce ambient noise level instead of trying to make the system sound louder.
Cheers,
Sid