Hi adi. Speaker sensitivity is a standardized measurement used to describe how much sound pressure will be generated by a speaker under specific circumstances. The standard requires that the speaker be driven by 1 watt of power with a calibrated microphone placed 1 meter in front of the system, both of which are placed in an anechoic chamber to eliminate the effect of "room gain". A speaker's sensitivity, then, is a function of its efficiency; how much do you get out for how much you put in. Most speakers are highly inefficient, on the order of 1% or so. To illustrate, an experiment was done a number of years ago. The acoustic wattage (figured in dynes per square centimeter) of a concert tympani was measured at 28 aw. With the average speakers efficiency, it would require 2800 watts of amp power (and enough speakers to handle it all) to duplicate the original power of the tympani. You can see, then, how important a speaker's sensitivity rating becomes if you are considering an amp purchase. The more efficient the speaker is, the more sound pressure you'll get for a given wattage input. However, don't get hung up on sensitivity. Most speaker will range from 86db to 91db; not a big difference. (It is generally accepted that the smallest perceivable change in volume in the average ear is equal to about 1db, with 3db being what happens when someone says "Turn it up a little bit") I think you would be happier with a speaker that sounds better to you with a lower sensitivity rating than one that was more efficient but less pleasing to your ear. Also, consider this often overlooked fact: doubling the volume (a 10db increase) does not require twice the power... it requires 10 times the power! So, if you are listening at an average of 2 watts and double the volume, it requires 20 watts; an 18 watt increase. Double it again, and it requires 200 watts; a 180 watt increase. You can do the math from there and easily see why a 100 watt amp is one of the most useless products ever created. So, yes, sensitvity is important, but not all-encompassing. Use your ears; the salesman is not going to be listening to your speakers, you will. Hope this helps. Luck...Jeff