Here is a quote from the JL 500/1 instructoins. Its one method to do what Mike is suggesting.
"4) Set the source unit volume to 3/4 of full
volume. If the amplifier is being driven by a source
unit’s dedicated subwoofer output, also adjust the
source unit’s subwoofer level control to 3/4 of
maximum output.This will allow for reasonable gain
overlap with moderate clipping at full volume."
From:
http://www.jlaudio.com/amps/pdfs/500_1_MAN.pdf
Page 14...
Its step by step instuctions. But the AC Voltages may not be correct. I suggest looking in your own manual for the correct ones, or contact the manufacturer.
I dont know if this helps but I thought id put it up anyway.