Just a bit confused. Why do amps have an impedance switch? I know what they are supposed to do, ie speaker load tolerance etc. But.................. SMR reviews I've read in the past have not been too keen on seeing them on the back of amps implying a poor 'quality' power supply in the amp. Switches like those are found typically on the back of Yamaha amps and the new Arcam AVR300. IMHO, I wouldn't have said they are bad amps at all, in fact, the total opposite. I've owned a couple of Yamahas and found them to be pretty good. Their new AZ9 looks to be a total monster in that dept. So the crux. If the switch is frowned upon, why include them on good quality amps. I'm sure I've seen John Dawson comment here on the forums about the new AVR300 being a ground up design, with a lot of time invested by him in it. Surely contradictory if the switch is really a bad thing.