Yamaha DTXpress/DTXplorer/DTXtreme

Bry,

Headphone choice is probably the most critical to the
volume and sound quality. I have 2 different sets of
Sony studio headphones that work great. I don't have
any sound or volume issues. I've seen these on ebay
ranging from $15 to $60 used, to $35-$85 new. 

To add to Ed's suggestions,when I first got my used
set, the guy said to use this little amplifier that he
included becuase he could'nt get satisfactory volume
from his headphones. It was called a "BosstaRoo."
Radio Shack and similar places have them. They cost
like $10 or $15. That fixed the problem becuase he had
cheaper headphones. But with the Sony headphones, I
get good volume and disconnected the booster. 

Most important, follow Ed's suggestions first, which
should be done anyways to see if its a hardware or
settings issue. Ed's knows his stuff!

Post your results to what steps you took and if it
solved the issue.

Ern