mud also recommend learning a little about impedance curves. These curves are much more important than a sensitivity rating if a speaker. Also realize that is no real standard in which the speaker industry measures
Good point's! There's so much focus on speaker sensitivity levels (With little clarity on how they are derived) . It's really the impedance load and curve pattern that determines how hard the amplifier must work. Sensitivity will influence how loud a speaker can go for a given amount of applied wattage.
Both parameters are useful to know but it seems speaker impedance and its impact is under appreciated.