It isn't much, but enough to be noticeable. If you convert dB to multiples, you can see that every dB change will result in significant change in the amplifier power requirements in terms of "watts":
If your current power requirement is 100 W, 2 dB higher speaker sensitivity will drop the requirement by 1.5849 times, to 63 W.
Conversely. if sensitivity is 2 dB lower, power requirement will go up to 158.5 W.
Speaker's sensitivity, and distance have a lot more effects on power amplifier output requirements than a lot of AVR owners may expect.
dB | Multiples |
0.000 | 1.0000 |
0.500 | 1.1220 |
1.000 | 1.2589 |
1.500 | 1.4125 |
2.000 | 1.5849 |
2.500 | 1.7783 |
3.000 | 1.9953 |