Okay, my setup has been the following when playing live shows with my band.

I play the M-audio keystation 49e which is hooked up through the USB of my PowerBook G4. I ues software such as Reason and Miroslav Philharmonik as my sounds. THEN I use the the headphone out to a keyboard amp(with a 1/4 inch to 1/4 inch jacks cord that has a 1/8 converter so that I can plug it into my headphones OUT on my Powerbook.

This setup ain't working for me. When I play most instruments(piano, harpsichord, etc), the lower keys are so much louder than the higher keys that I cannot concentrate on performance. Instead I am riding the volume levels.

How I can fix this? I only have a headphones out jack as an out on the Powerbook G4 and it isn't delivering stable levels to my amp.

I also own a Tascam US-122 which I use with guitar stuff, but haven't figured out if it could help me send the signal from my computer to an amp in a better way. I am really frustrated.