Well, you've solved half of my issues! You were completely right about the keyboard volume controls. I had completely forgotten about those! It was set nearly as low as it could get. Problem solved!

At home, I have self-powered (Klipsch ProMedia 400) speakers. The problem is that I would like to be able to adjust the volume using the speaker volume knob, but if I set the volume of everything on the computer as low as I can get it, I still only have about 20 degrees of travel on the speaker volume knob that takes me between mute and full blast.