This still feels like yesterday's repair, even though it was tonight when I did all this.
Since I had the final module out from yesterday, I hooked power to it to test. I first tried the driver, and it didn't trip the circuit breaker. Then I tried the high power amp and it tripped the circuit breaker immediately. Fearing the worst, I embarked on the long process of removing the finals (which was not fun because of how they were stuffed in there.
So after removing these, I put them on an octopus tester, and tested them. The results are interesting. It also says that one or both of them is likely bad. These things aren't cheap, but with how much of a pain it is to remove them, the smart thing would be to replace both, since one went, the other is likely not far behind.
Note: the upper-left and middle-right are nowhere near the same:
Next up: replacing the transistors and powering the unit back on!