I'm using Behringer A800 power amps (Class D) for everything except the front two speakers in my setup - they do me just fine powering the surrounds and heights. They are two channel amps but can be bridged for mono, and they also offer a good degree of flexibility with RCA, TRS and XLR outputs ( I use the XLRs into my Marantz AV7705). Not strictly a true hi-fi solution but I'm happy with them.
Until I changed my system recently I was using a Rotel 1060 6 channel power amp, which did a good job for my Atmos / ceiling speakers.
I upgraded the amp for my front 3 with a Procella amp, so now use my Anthem A5 for the surrounds and Atmos, so the Rotel is no longer required. The Anthem is definitely overkill and doesn't obviously offer much more than the Rotel on those speakers.