Volume does not = power being produced. Amp always makes the same amount of power. As said by others, amps are stupid, they don't know what to do so they just keep making a set amount of power depending on voltage, impedance, and gains. The amp doesn't say "OH HAI HE'S TURNING THE VOLUME DOWN, I'LL BE SURE TO CREATE LESS POWER"...
Edit: If you meant "....time you turn the GAIN down..", then you are correct. If not, read the above.
Dirty power? You mean signal? No such thing as "dirty" power..