"Digital" converts the analog signal to digital; applies the same bass management, time delay (speaker distances), and channel trim; and then converts back to analog. "HPF/LPF" leaves the signal in the analog domain (no digital bass management, time delay, or channel trim) but employs an 80Hz analog crossover network to redirect low frequencies from the full-range speakers to the subwoofer. "HPF/LPF" provides a cleaner and simpler signal path, so it's worth trying to see which you think sounds better. If there's no difference in your system, the "Digital" setting would allow you to skip calibrating the SACD player (leave channel trim at zero and don't set any speaker distances) because the 1070 will do it for you. In both cases, you would want to disable any bass management in the player (set all speakers to "large" and the sub to "on") since you are getting bass management at the 1070.