In AHI prefs the button where you select a unit is not a setting. With the button you select the unit you want to change the settings for. The settings for all units are saved when you click on Save.
So, set the button to music unit, then select Paula:Stereo++ and 22050 Hz. Now set the button to unit 0, select Paula:Stereo++, 22050 Hz and 2 or more channels. Repeat this step for all the other units. Depending on the AHI version more channels will reduce the volume.
In AmigaAMP also set the decoder to 22050 Hz.
