Hey Michael,
Per Axiom's pamphlet that comes with the subs, they recommend setting it midway of the 9o'clock position to start. So on the 500 and 600, that is pretty low, around 6-7 o'clock position. Keep in mind your still getting the full 500 or 600 watts of power no matter what you have the setting on. Alan mentioned at one point to put the receiver level on 0dB for the sub, and then adjust the volume knob on the sub up/down until you get 75dB's or whatever you calibrate to...Also, the trim level normally should be used on "flat" for larger rooms and for flatter resonse, but you may want to experiment with half and full if your getting to "MUCH" bass, these may help tame that...:)
