With any of our amps (have to put the caveat "when built properly" as I've seen people jumper the safety stuff) and the Stax ones the damage potential would be minimal. With the bias, sure it is 580V but it's based on a very current limited voltage doubler circuit plus the 4M7 high voltage ballast resistor on the output will prevent any damage.
The amp section could deliver some real hurt though, +/-400V or upwards power supplies with the amplifiers being able to swing almost from rail to rail meaning you could see ~1500Vpp or more at one output. This plus generous class A biasing means there is a lot of power at play here, hence the 5.1K output resistors. If there would be a short to ground (i.e. you) they would take off the worst of it.
Now look at Woo Audio, Cavalli plus other amps and these protection provisions are just not there.