The volume shouldn't have had much (if any) effect on the heat generated in the empeg. The output stage isn't handling much current at all, leaving the power stuff to the amp. The only way that volume can be a factor is if your empeg is mounted next to an exteranl HU that you are using for amplification...then the heat can transfer into the empeg. But loud volumes often generate less heat in an amplifier than quieter volumes. You will often find that around 1/3 volume generates the most heat in an amplifier.