The PL6s are over 20 years old, some of the parts are no longer made and likely remaining stock is with QSC...
While they are old, I think they came out about 1999 or 2000, making them 13~14 years old.
But yes, QSC is running out of parts and, at least for the 6.0PFC/6,0II, the PL380 is a viable replacement AND they offer that neat rebate.
I am looking at picking up a Crown MA5002VZ but I'm worried it won't have as much grunt as the pl6 based on specs.
No, I'd say that the old Crown MA series is aging worse than QSC amps. And Crown considers them less of a urgent repair than a current model.