I have to laugh at the garden hose-sized power cables
Me too. The weight/stiffness of some of those cables is enough to pull a lighter-weight piece of equipment off the rack.
Of course, cable supports will alleviate such a problem!
When it comes to the mains-power side of things, I offer this: when I provide a PA system for a festival, I'll make recommendations about the generators or mains supply to ensure proper system performance. Occasionally, those recommendations are heeded. For context, I'm in the UK, where the mains supply is 240V nominal, the typical mains outlet is 13A-rated, but the fuses in the plugs will allow higher current draw for short times: you can pull 30A for one second!
The PA system includes a digital mixing desk, and 3x Powersoft amplifiers: T604 (biamped mains), T602 (subs), T304 (stage monitors). Plus all the musical-instrument-related gear (amps, pedals, etc). If pushed to their limits, the Powersoft amps will put out 15KW total, for short bursts. Fortunately, live music is peaky and the average mains draw is fairly low.
I've had to run that system on the end of around 150m of extension leads when the supplied generator ran out of oil and seized. To call the mains supply "squishy" would be an understatement. I could watch the mains voltage drop as I pushed the master fader.
Another time, a cheap 3KVA generator was supplied, and that thing had basically zero voltage regulation. The PA system draws relatively little current at idle, but when the kick drum hits, it'll pull a LOT, especially if I bridge the T602 into 4ohm. As a result, for each kick drum hit the mains voltage would drop to around 200V, and then the generator would try to recover. Demand, however, had dropped, so it'd overshoot to 260V. Repeat for every kick drum hit.
The situation improved somewhat when 1KW of filament lights were connected up - at least that way the generator would never drop to somewhere-near-idle.
In the case of the generator, I'm certain there was a lot of noise and other crap on the mains supply. In all cases, the PA system didn't care. No extra noise, no ugliness, no impression there was anything wrong with the mains supply in any way. It just kept on working.
Given all of that, I would suggest that if your audio equipment is in any way upset about having a subpar mains supply, it is broken. The power supply filtering is not doing its job, and it should be returned to the manufacturer for diagnosis.
Chris