BTW, what's your take on the high chassis voltage, higher with the correct polarity?Well the lower chassis to equipment ground voltage is the correct orientation polarity for the amps. Seems odd to me both amps would have the primary of their power transformers wire incorrectly.
02-01-09: Maril555
By chance are you using aftermarket or home brew power cords on the amps?
If so it could be the cords are wired wrong.
The wiring on the 3 wire NEMA plug could be right but the hot and neutral on the IEC are reversed. Easy to check with your multimeter. Just pull each cord from the amps and check the continuity from end to end on the pcs.