Keep in mind that while you may have some beefy 100w/ch amps, the long term average power, even at high volume, is about 2w to 4w.
A 4 ohms speaker relative to an 8 ohm speaker does get the same voltage, but for a given voltage it draw twice as much current. So, referring to above, the average power is 4w to 8w, instead of 2w to 4w. Though 4w to 8 ohm would be substantially loud.
Power = Vots²/Resistance
So, if you apply 12 volts to 4 ohms and 12v to 8 ohms you have this -
P = V²/r = 12²/8 = 144/8 = 18 watts
P = V²/R = 12²/4 = 144/4 = 36 watts
If you have a Volt Meter that has a needle rather than a read out, you can put it on your speaker terminals and get an idea of the average voltage, then using the formula above, you can calculate the average power. It is not going to be has high as you think it is. If fact, I suspect it will be closer to 1w to 2w.
Remember speaker Sensitivity ratings are with 1w (or 2.83v). That will drive a speaker to 85dB to 95dB depending on the speaker. That is pretty loud. So, despite needing 100w/ch for music peaks, your average power is very low, far lower than you might think.