This thread is old but i'll still try to put in my 2cents, I think hawkson was looking for something similar to a car stereo setup, if that was the case then the rear speakers output level will need to be reduced significantly in order to create that echo effect you normally get from concert or orchestra. I don't know if the HK525 have Time-Delay or not but this little devil play a major role in setup like this, otherwise you'll more than likely trashing the frontstage, and throwing off the imaging. An extra pair of M22ti running in the rear is overkilled, I would opt for a pair of surrounds or M3ti for the rear channel.
