Yeah, there are kind of a few dimensions to what you need to consider.
The most important thing (in my opinion) is to be able to get all the power out of the Stereomour that it can offer with the sources that you have. If you're leaving 2-3 Watts on the table because the source voltage is too low, then changing to more sensitive speakers doesn't really address the core problem.
On the other hand, if you find yourself bottoming out the speakers, or clipping the amplifier, then more power or speakers of higher sensitivity would be worth looking into.
