Ardour working volumes question

[varpa]

You have issues with monitoring - see http://manual.ardour.org/recording/. If your mixer can be configured for direct monitoring that would be best, i.e. the signals being recording are sent directly to the outputs and bypass the computer which gives the lowest latency.
It does not sound like you use the mixer for playback, so you'd have to figure out a way to go from the mixer to your amp. If that is not possible, then you can set up Ardour to do monitoring as described in the link above.