HSU has had a tough time, as has Adire the woofer supplier. I have not heard what the issue is with the plate amps, but as far as I know HSU is doing everything it can to get replacement parts into everyone's hands.
Production variation seems to be an increasing problem; unfortunately human hearing and perception of music don't allow as much leeway as other industries might have.
All we can do as consumers is support companies who try to fix these issues when they arrise, and at least make note of those who don't.
