You mention speed: speakers' efficiency does not necessarily mean speed.
As to db, +6db in sound level is perceived twice as intense (all other things being equal)... 1db being the level of perception (or perceptible change in intensity) of a "normal" ear.
I suggest you favour speakers whose sound you like -- true, the more efficient they are, the less horse-power you'll need to drive them (which doesn't, unfortunately, make quality amps very much cheaper).
Cheers!
As to db, +6db in sound level is perceived twice as intense (all other things being equal)... 1db being the level of perception (or perceptible change in intensity) of a "normal" ear.
I suggest you favour speakers whose sound you like -- true, the more efficient they are, the less horse-power you'll need to drive them (which doesn't, unfortunately, make quality amps very much cheaper).
Cheers!