Strange op-amp circuit FM radio
The opamp outputs are connected as a 'bridge'.

The caps cause a 180 degree phase change in the inputs, and the outputs are therefore 180 degrees out of phase as well. 

You can therefore get double the voltage swing on the loudspeaker for the same battery voltage.

P = v^2/R

Double the voltage, 4 times the power into the same load! (provided you can manage the current)