I have figured out how to fix the quiet dialogue for people with non-2.1+ speakers (i.e. 2 speakers or headphone users).
Goto Documents > Bioware > Dragon Age 2 > Settings >
Open up DragonAge.ini
Look down a few lines till you see these
CutsceneListenerRadius=1
ListenerPositionOffset=0.5
Change then 0.5 to 0.1 and things will sound a lot better when speaking to people
Tested and works even tho I did not really need to. Just backing up DABs post.