It;s how loud your speakers will play given a certain power input. This is usually labeled dbW/M or decibels per watt per meter. 89 means that with one watt of power, your speakers will be 89db at one meter. This is around average or perhaps a couple db lower, I would think. This doesn't have bearing on the quality of the sound, but does affect what kind of amplification you might need to power them depending on your listening level.