Also how much better is the dac that's in the Dac-9 compared to the dac in the Dac-100?
Looks like you have ask a couple questions:
1) The DAC-80 is the same DAC as the DAC-100 except it doesn't have the Headphone Section, and it has 4v rms output instead of 2v rms.
2) The DAC-9 is presently the "Flagship DAC" and will have sonic differences available to you if you have a System revealing enough to hear them.