Help rotel pops when turning on and off

Not sure how loud the pops you are hearing are but I have owned several amps that made loud thumps when turned on/off. Rotel RB-981, Adcom (three different models) and a Portal Panache all made annoying thumps. The Rotel also hummed through the speakers. I owned two of the Rotels and they were identical so I figure it was their nature. Basically the issue is that these models don't have a circuit which mutes the the output until the power supply has settled.
It shouldn't harm anything but it is annoying. Unfortunately the only solution is a different amp. Ask the seller questions concerning operation before buying.

I'm just guessing but when you turn your Sony receiver on you probably have to wait a few seconds for it to actually produce sound and also before it produces sound you will hear a soft click. That click is the protection circuit ensuring the power supply is stable before providing current to the speakers. Not all amps have this. Your Rotel doesn't have it.
My Portal Panache would thump when turned on and it would also keep producing sound for 5-10 seconds after it was powered down if the cdp was still playing. This is caused by the power supply capacitors keeping the amp operating while they discharge. As I said before it's not harmful but it can be annoying.
As for leaving the amp on, it's your electric bill.