If someone is using fully 2-speaker stereo setup or 2.1 system setup.
There is no real benefit from adding a center speaker as in 3.1.
Plus if the music is not recorded in surround format. Still no benefit.
Using stereo music from AV-amp with 3.1 speaker.
You would get a combined/mixed L+R from the center channel so. It’s not as good as true stereo.
It will be little louder since one more speaker = more noise or sound.
Works just fine on trance, edm, tehcno and so on Plenty of noise.
When using and playing surround music, source device understands the media its surround. Amp knows is surround material.
Then you will get little nicer sound stage with true stereo.
BUT the speakers should be equal also. 3 very similar speakers or 3 equal speakers so the stage sound is optimal for the surround music. Moving left and right and so on. Depends of the music.
Still is it worth the effort… is another thing.
Makes more sense going full surround setup and not just stop to 3.1.