*That* is what the guitar tech told me, not what *I* said. I was wondering if the EMGs would work with a 250k or 500k pot in the first place. I have little doubt that what he told me was wrong, for the very points you stated yourself. But the problem would be so much easier if I'd bought them first hand, but I got them second hand so I don't have access to the pots. Thus the question if they'd work, and if they do, how well. The many different answers I've got shows its not quite as straightforward as it seems to be.
There is a little hope, though. I found out from a friend that the guy I was talking to isn't the actual technician, but sort of a salesman guy. The guy doing the actual installation is someone else. Hopefully, I won't die of an electric shock. Btw, what do you mean by an amp running off "dirty" power?