I actually went back and read the original starting post.
There is little relation between amp power and speaker power rating in the real world. There are various amplifier power ratings that provide steady-state sine wave output but underestimate the dynamic (peak) power available from the amplifiers that add significant headroom in actual use. I do not think there are any defined standards for rating speaker power and it is usually just a number. it would be nice if some sort of graph or at least max power to each driver was presented, but I have only rarely seen such information. So you are left to guess.
Ages ago amps were small and tended to clip readily, and speakers were much less robust than today. Today run-of-the-mill AVRs put out around 100 W cleanly and modern drivers (LF, anyway) easily handle that much power on musical (or movie) content.
I would determine the sensitivity of your speakers, where they are placed in your room and how far away you are from them, and use a calculator like the one linked below to estimate the power you need to reach the volume you desire. Now you can decide what amplifier power is needed and if the speakers can handle it. If the speakers can't, you need different speakers with higher sensitivity, higher power rating, or both. Note most speakers distort heavily well before reaching their peak ratings. If the speakers can handle the power, you can estimate how much amplifier power you want, remembering every 3 dB doubles the amplifier power.
A pair of 90 dB/W/m speakers 12 feet away, near the side walls, driven by a 100 W/ch AVR can reach nearly 105 dB at the listening position and that is plenty for me. I still need my ears for my band and orchestra gigs. I think a lot of folk would be surprised by their listening levels; probably much lower than they think. 80 dB is loud! Of course loudness wars are always interesting...
I generally decide upon the speakers first, based on how they sound and specifications like sensitivity, then pick an amp sized appropriately. These days most AVRs have no problem driving most speakers in most rooms to levels well beyond what is safe or sane. But of course nobody is average...
All IMO - Don
SPL calculator: http://myhometheater.homestead.com/splcalculator.html