There are two factors that determine the maximum output power: supply voltage and speaker impedance.
For the supply voltage, do not exceed 24V.
For the speaker impedance, do not go below 2 Ohm and only if the chip for that channel is PBTL coupled. For the sub-channel of a TPA3116 2.1 amplifier, this is often the case.
NB: Make sure your power supply is powerful enough (can supply sufficient current).