HD sound

I have a dish 811 receiver. When I watch TV I have a headset that I use because of a hearing loss. When I watch a program in sd I can most generally understand them but in HD it seems that the music is much louder and its harder to understand. If I hook something into the optical output would that improve the sound?

Does ABC transmit closed captioning for Lost and Invasion. The ABC affiliate in Denver does not transmit it.