I have an SB220 amplifier that runs nicely at 1KW with 100W input. There are times when I don't need 1KW and would like to reduce the drive and take the amplifier down to say 500W. I have heard that these amplifiers do not operate properly with reduced drive. Is this the case or can I safely reduce the drive to say 50W and still use the amplifier running about 500W out? Thanks!