The difference between stereo receiver vs amplifier?

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I have a pair of Klipsch RP-160M (impulse black friday purchase) and going to stream with Chromecast Audio.

I'm looking at a decent stereo receiver like the Onkyo TX-8140 mobdro kodi.

I'm also looking at the Yamaha R-S500 stereo receiver and Yamaha A-S301 amplifer. If I'm using a chromecast audio, I'm not sure if there is a difference between the two