A 16 ohm speaker demands much less from the power amp than lower impedance speakers do. You will have no problem at all driving 16 ohm speakers with an Insight 240EX amplifier.
Wayner is rebuilding an old pair of AR loudspeakers. I recommended that he replace the old capacitors with newer film capacitors of the same uF. He is insistent that replacement capacitor(s) have the same voltage rating as the original capacitors. I told him there is no reason why he cannot use higher voltage rated capacitors. Apparently he thinks that if he uses different voltage capacitors, he'll somehow mess up the crossover, shift the crossover frequency. I succinctly informed him that voltage really doesn't figure into the equation, not when doing the math for capacitive reactance.
A typical fim capacitor might be something like 250 volts, which provides a margin of safety way more than will ever be needed.
Seriously, if you have an amplifier capable of delivering 250 volts, you better worry about the tweeters blowing before worrying about any supposed shift in the crossover frequency.