No, there are more. But auditing an S&P500 corporation is pretty complex. I am not in the auditing S&P 500 corporation business and it looks like there may be six - but the Big4 literally seem to do 491/497 companies. I’m not sure I am too concerned about the auditing quality of the Big4 tbh though…

Enron’s problem was the “consulting AND auditing” mess with conflict of interest if I am not mistaken.