dont worrry about it. it is safe because when an amp is rated at 200w per channel, doesnt mean that it will output 200w constantly.

you may only get max 200w when there is a sudden burst of loud sound from the movie. even so, it will not damage the speaker as these are very short burst of just few millisecond.

it is more worrying if the amp is underpower as this will cause clipping to the amp. when an amp is operating near clipping output, distortion will be exponential and these distortion will damage your speaker.

most of the good speakers do not write the rated power but instead will write the sensitivity of the speaker.

the lower the sensitivity (example:86dB and below) the harder it is to drive the speaker and will require lots of power to play it loud. a rough estimate: you will need to double the power from 50W to 100W just to increase the loudness by additional 3dB.

so if you have a speaker which is about sensitivity of 85dB, you will probably need about 200W to play it well but if you have a speaker that is about 91dB, a good 50W will be sufficient.