Personally i would take the dirt out of the filter and see how the boiler gets on afterwards, maybe put cleaner in the system for a few days, drain down and refill.
The problem with power flushing is that it is never a definitive answer to your problems, i am not a great advocate for them because you are charging a customer for a day of a plumber on site as well as the machine being charged out and you might have the same problem at the end.
If your system is so bad that the boiler is over heating, is making a noise and rattling then i would advise that a power flush is not the way to go and you should actually be looking at installing new pipework.
The problem with power flushing is that it is never a definitive answer to your problems, i am not a great advocate for them because you are charging a customer for a day of a plumber on site as well as the machine being charged out and you might have the same problem at the end.
If your system is so bad that the boiler is over heating, is making a noise and rattling then i would advise that a power flush is not the way to go and you should actually be looking at installing new pipework.