For what sources? If streaming and 55 watts are enough, the Sonos Connect: Amp is the simplest solution. One little clean and good looking box is all there is to it. Of course not for the ambitious audiophile.
Any small integrated with digital inputs can be turned into a slick streamer with the digital output of just a Chromecast Audio. I did that with a tiny Ava Maestro 50 in our bedroom. Its important additional advantage is that it has an auto on/off facility so you can hide it out of sight (it is a cool running digital amplifier). Its only downside is that with about 2x25 watt (if that) power output is too small for more ambitious speakers or larger rooms. It is just enough for the small 85dB Wharfedale Diamond 9.0 in the bedroom, but it would not properly drive my Harbeth P3ESR.