Current, Amperage

No doubt elevick's math is correct, however there is more to consider. Those SPL's are at 1m, and the further away they decrease, but there's 2 speakers and room gain. If it's a 4 ohm speaker, the sensitivity spec is at 2 watts unless it states 1 watt. If nothing is stated or it says 2.83v, then 2 watts, so a 1 watt rating is 3db lower. The power necessary is for a maximum peak SPL, not the average. Depending on the type music, some peaks can be as much as 20-25db higher than the average.

The recommended minimum power of this speaker being 40 watts is likely due to it's varing impedance, 8 ohms nominal, 2.9 ohms minimum. But that wattage spec can be misleading as well. I'm sure a 30 watt Pass would have no trouble, where as a budget 100 watt receiver would struggle.

current and wattage, courtesy of Atmasphere

http://www.atma-sphere.com/Resources/Common_Amplifier_Myths.php

@lilmsmaggie 
yes, sorry, my ‘pre-amp’ is a VTL 2.5. 
I had an Mcintosh MC252 but sold it a few years ago and my stuff has been in storage. I’m now looking for a new amo as I want to setup my system again. Not sure I want to soend that much again on an amp. 

I also had seem the Focal ‘power suggestion’ of 40-250, but that is a big range. 

Bottom line, will the current/ amperage in a less expensive amp of 100-150 watts be enough to provide the right power?  Rotel, etc? 

Also, what about Class A, A/B, D - does this come into play and is it a big variable depending on your speakers, etc?

Thank you.

Already seeing a bunch of confusion....

91.5 dB is NOT the 1 watt efficiency of those Focals at one watt. That's their sensitivity to 2.83 volts. I'm sure they've got that characteristic Focal upper bass impedance dip down around 3.5 ohm. That means their efficiency drops off, which you'd hear if you used a current source amplifier, which very few are. So, when figuring out what kind of wattage you really need to drive them, you should figure how much current that load will draw at the voltage required to produce the dB you want at your listening distance. At 12 feet that going to be a good bit more than 8 watts. 

Most focals require extra current in the 100Hz range due to relatively low 3 ish impedance. Not an amp killing situation, but I do find that they sound a little soft in the bass unless the amp is stiff.

Don't need a high power ratimg, but they will are relatively "discrimimating" when it comes to amplifier current delkvery. An unfortunate trait for otherwise highly praised and affordable line