Always get speakers with lower watts than your amp.

If the amp's power rating is below that of the speaker, the amp will try too hard to keep up, if you like, with the speaker which means the amp will 'clip' which could possibly cause more damage than over-rating the speakers.

If the amp that is more powerful than the power rating of the speakers, provided the power rating of the amp was not a great deal more than the rating of the speakers (50 watts +) then there should not be a great problem provided you as the customer are sensible when it comes to running the speakers. That means, don't crank the volume up too much, but that's not anybody's intention to have a hi-fi system anyway.