have you checked the sound on windows?
have you checked the sound in whatever program you're using to play your music?
have you checked your gains on your amps? (better yet, have you set them properly?)
are you sure that this isn't just your recording?
do CDs play any louder?
if you're reading that a line driver does nothing, I'd like to see that thread please! Post up a link if you can.
If you're not getting your amps the voltage they need, then they can't produce the volume in the first place. This is where many people rely on the adjustable gains. They are there for this reason, but many times, people abuse them.
If you don't have anything to work with in the first place, then turning up nothing won't give you much of anything....make sense?
btw - I know that on the M10000, the voltage out from the mobo on-board sound is only like .5v....that's hardly anything
do you know what the voltage out on the X-FI card is?