Really don't matter, unless you buy
a) a really cheap amplifier with low power and poor power supply
b) 4 ohm speakers
c) Inefficient speaker ie 83dB @ 1W.
Most affordable speakers are designed to run with affordable amps, usually once you go higher end, they are sometimes 4 ohm so you need a higher quality amp. You can use a amp that is too powerful, and a amp that is low power. But for the latter you have to be careful it's not clipping, you should be fine unless you have something like a 10-20W amplifier.
But it's good to have reserve power, I use 60W amplifiers, most powerful are 180W per channel (and not AV amplifier rated, true power)