If you use wired speakers you will still need an amplifier. If you used a two channel amp you will need at least an impedance matching speaker selector. If you wanted to control volume in for each room you would need a volume control for each room. Some of these have impedance matching so you don't need the selector if you get these.
If you wanted to play different sources in each room you would need a multi-zone amplifier and a way to control each zone.
You would also need at least one box to access internet radio, streaming services and files.
Overall it isn't necessarily cheaper than the stand alone speakers but can sound better and play louder.
Using stand alone speakers you can do one room at a time without having to buy a central...