A "dumb" question about power ratings?

I'm no engineer, but I believe that our Revel Gem speakers have an impedance of 87db, which is whiy the dealers I talk with to recommend an amplifier that puts out at least 100 watts. If this is correct, does this mean that they are suggesting 100 TOTAL watts? Here's where I'm a little confused: The solid state amps I've looked at like the Levinson 334 or Ayre V-1 are "rated" in terms of total watts available. In this example 125 watts and 200 watts respectively. If that's right, then 1/2 of the total wattage is available to each speaker. A 200 watt amp provides about 100 watt per speaker - right? The reason I ask is that mono-block tube amps and the Pass 'class A' amps seem to be rated by the watts put out by each mono unit. If a mono-block tube amp is rated at 50 watts, then that means 50 watts for each speaker, or the equivalent of 100 total watts available in the system -- is this correct? Put simply, is a mono-block tube amp rated at 60 watts roughtly equal in power to a solid state amp rated at 120 watts? I find power ratings and figuring out how much amplifier power is optimum a bit confusing. I suspect this may be a dumb question, but I just want to make sure I understand the ratings correctly. Also, I'd love to know how to make the decision of how much power is enough. Is it simply a mathematical question dependent on how loud you want the speakers to play? Or do other sonic factors come into play? I've read about tube amps that only put out 15 watts, which seems miniscule to me. Would my Revel Gems even operate running off a low powered tube amp? What would they sound like? This is America, after all, isn't more power always better :-)? I will certainly appreciate your insights! Sincerely, Kurt