Managing volume

Listening to some music, I realised I have 5 volume controls, all completely independent of one another:

1. The volume control in the audio player
2. The OS (Windows) main volume control
3. The USB / Direct mixing knob on the audio interface
4. The volume knob on the audio interface
5. The volume knob on the amp

It's a bit too much control really, as if the sound is too quiet there are 5 places you need to check the volume setting.