Yamaha DTXpress/DTXplorer/DTXtreme

Following on from a post I left recently which asked members what 
they played their DTX2 through when playing live. Have members got 
any comments about the direct headphone-amplifier contrast in terms 
of sound quality? I did once use a DTX2 at a blues band rehearsal and 
found it to be lacking, although I was only playing through a combo 
amp and the other guys were very LOUD! What struck me most was the 
lack of volume on the hi-hats. What advice would members give about 
getting the hi-hat volume up to an acceptable level?
Look forward to your comments
JonD
Leeds, UK