I have an Anthem MRX700 receiver, Focal floor standing for front speakers, centre and sub as well from Focal. Reused some old panasonic home theatre speakers for rear. The setup is in use for couple of years but the receiver has failed couple of times with "Amp protection powering off" message every time when I tried to watch a movie with good surround effects. I had to take it to the supplier and it was repaired as long as it was under warranty. Now it failed again and they blame the speakers for over driving the Amp and ask me to pay for fixing it. I have checked all the obvious aspects like wiring for short circuits etc. I have a doubt if my rear speakers are not matching with the specs of the Amp or front and thought would upgrade them with some second hand KEF speakers. Before proceeding further, I would like to know if I'm doing anything wrong in my setup, what aspects I need to check (eg: Impedance, type of connectors for cable?) and if there are any options for me to prevent a faulty external source from affecting the Amp. Any suggestions would be really helpful.