The M20d has all the eq you need. Turn the Bose's mixer to a flat position and try to get a better sound from there. If you have any kind of eq applied from the speakers, the internal presets will be offbase from their intended settings, because they are also altered by the eq  from the Bose unit and that may be wrong. For ex. if you have a mid scoop on voice and the Bose also have one to make the speakers sound more hi-fi (smile eq), then the voice is even more affected from this.