Speaker specs: Sensitivity, & Amp match

Elevick is correct. A 10db increase in SPL will only be double the volume (what our ears hear and brain perceived to be).
The usefulness of all this becomes becomes apparent when we think about how the ear perceives loudness. First of all, the ear is very sensitive. The softest audible sound has a power of about 0.000000000001 watt/sq. meter and the threshold of pain is around 1 watt/sq. meter, giving a total range of 120dB. In the second place, our judgment of relative levels of loudness is somewhat logarithmic. If a sound has 10 times the power of a reference (10dB) we hear it as twice as loud. If we merely double the power (3dB), the difference will be just noticeable.

Regards,
Rich

I actually thought the perceived increases were exponential, not logarithmic, but I'm far from an engineer. I just know my shorts will taste like s**t. Someone check audioasylum to bail me out please.
Keep in mind that I used the word "perceived" since I know a physicist will tear this statement apart otherwise.

Newbee: the difference lies in what you're measuring. If it's sound PRESSURE, 6db means "double" {20log10(p1/p2)=db}. When it comes to watts, 3db difference means double (or half, as it were).
Minimum "perceptible" diference in spl has been said to be 3db; if forewarned, I can detect smaller changes in spl, so can most of us.