To be clear the monitors have the built-in speakers, and they have left/right inputs that match to the machine's output audio ports.
You can also get left/right external speakers that plug into your machine's audio ports to get the same (and probably better) effect.
I said "technically, yes" originally because the way the Amiga outputs stereo sound is a little odd. It's more literally outputting independent left and right channels with no real cross mixing. This is most apparent if you ever decide to use headphones with your Amiga. There is a new product out there that solves this issue (which I've been looking at getting for a while now) called the KA71 made by RastPort.
RastPort:
Amiga sound chip Paula sends two of its four audio channels to stereo left channel, two to the right channel. They are fully separated, which is annoying especially when listening with headphones. KA71 can mix stereo channels at a level adjustable with a knob, from full separation to mono output. It can be also used with computers having monophonic audio, or to mix two computers simultaneously playing parts of the same song. Of course one can also use KA71 as a regular headphone amplifier with smartphones, music players, computers and other sources.
But to the original question, yeah - there were a lot of stereo monitors made by Commodore.