Sound systems would wire in series and the amps would generally double the wattage.
So for a well designed amp rated at 100w amp at 8 ohm's output connected to a pair of 8 ohm speakers connected in series to another pair would halve the impedance down to 4 ohm's and throw out 200w.
Wired in series these four 8 ohm speakers would present a load of 16 ohm's to the amp so it would throw out 50w.
A Krell KSA-80 would throw out 80w in to an 8 ohm load, 160w in to a 4 ohm load, 320w in to a 2 ohm load and if you are really insane 640w in to a 1 ohm load!
It does however weigh about 45kg and the Extinction Rebellion crew would be chasing you if you ran it below 4 ohm's. It could all be done with Class AB amps that weigh a lot less.
I think that made sense......