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.