Watt SPL?
Asking about Watts is the wrong question to be asking.
With Watts you are finding out how much electricity is being sent to the speaker, from there it depends on how efficient the speaker is as to how much sound actually comes out, and this is measured in SPL.
More relevant questions to be asking would be what is the SPL output of the speaker with 1 watt fed to it, measured at 1 meter, ideally with pink noise from 20Hz to 20kHz, rather than a 1kHz sine wave.
Or what is the maximum SPL of the speaker