Yamaha DTXpress/DTXplorer/DTXtreme

Hi, guys... I'm a brand new user, but I'm somewhat dissapointed
with the volume I can get from the module. I'm not talking about
the headphones volume, which has been discussed to death, but 
the volume I get from my amplifier.

My signal path is DTXpress to medium-hi class home amplifier (Mission
Cyrus One) to Bose Acoustimass loudspeakers. Although I maxed the 
volume control both in the amplifier and the module I get a VERY weak
output from the amp. If I use the headphones output from the DTX, I
get a *bit* more output, but distorted. I'm using the "Aux" input in 
the amp. The amp volume seems OK using any other source (Discman,
Video, Walkman, etc... even my BOSS GT-3 guitar effects processor 
sounds full and loud...)

Am I doing something wrong?... Are there any "parameters" to increase
the output volume?...

By the way, I connected it to a friend's Bass combo and it sounded
loud, full and rich! (DTX's mono output to amp's preamp input).

Thanks a lot in advance...