good question tommy!
i spent some time recently tuning my 320's by ear and they seem to be working well... my motors were humming like crazy and i don't have access to an oscilloscope so there wasn't an option for me. i spoke to the manufacturer of my milling machine. he said that's how they tune them! so... i fine tuned damping and gain til they were quiet. 40 hours of machining and they're ok. i'd be interested to know if this will bite me later on.