Power rating for speakers

Essentially nothing. These are approximate power ranges the speaker manufacture thinks are proper for the speaker. But amps vary tremendously in their ability to deliver power at different impedance's. Also remember that far more speakers are damaged by too little power than too much. Get the efficiency of the speaker , measured in db for one watt input. Increasing the output 3db requires twice the power. See if the amp you are considering has more than enough to drive the speaker to its full rated output.

Would mean if I played the music at a low level (say 10W) for a speaker thats rated 50-150w, I'd be damaging the speaker?

Would mean if I played the music at a low level (say 10W) for a speaker thats rated 50-150w, I'd be damaging the speaker?

No.

Please also see my response in the other thread in which you posted a similar question.

Regards,
-- Al