Classe' ssp-800 Weak sub output?

Make sure the volume for the subwoofer is turned up.

On your "home" screen, select "controls."

On the "controls" screen, select "system trims."

On the "system trims" screen, select "level trims."

Here, you can choose the subwoofer and adjust its level (upwards). Hopefully, it will be able to increase sufficiently to satisfy your requirements.

[add] To get an even greater effective increase, try turning down all the other levels -- that should make the subwoofer sound even more prominent.

I don't have experience with the ssp800, but have an older Classe model. Here, the level of each channel can be customized in the setup menu. Could be similar on your newer unit.