Power rating is not related to speaker quality. A speakers sensitivity will also play a large role. In case you're not aware to increase the volume of your speaker 3db it takes double the power. 3db is barely noticeable. In other words a 200wpc amp will play 3 db louder than 100wpc amp or a 50wpc amp will play 3db less loud than a 100wpc amp.
Speaker sensitivity can vary greatly. The average being around 88db for one watt at one meter. This is a rough estimate. If you look at various speaker designs you will see many that are 86db sensitive. Let's take a speaker that is 86db and another that is 92db sensitive like the person's above this post. His 92db sensitive speakers only need one fourth the power to play at the same volume as the person who owns the 86db sensitive speakers.
In other words the person above could have a 50wpc amp and match volume with the person who has 86db sensitive speakers and 200wpc.
I figured you're not aware of this or wouldn't have asked the question you have. Another thing to remember is that a power rating of a speaker is a very rough estimate. There's no standard and different speaker manufacturers will use different standards. It means nothing as to sound quality. Buy a speaker who's sound you like.
Speakers can usually play with an amp with more power than the speakers are rated for. Be careful and you'll be fine as long as you don't make the amp clip.
With a 100wpc amp with the speakers you're considering to hit 104 db you only need 32 watts. Of course this is at one meter but at say 10 feet where you may be sitting you'd still be into the 90+ db range.
With all that said depending on your speakers and amp this is only a rough guess. Some speakers need an amp requiring excellent current delivery while others like Vandersteen are usually an easy load, at least they used to be. Thiel's on the other hand you may want an amplifier with a more stout power supply. In the end buy what you like unless the speakers are very inefficient it's usually not worth worry about too much.Hope all this helps.
Speaker sensitivity can vary greatly. The average being around 88db for one watt at one meter. This is a rough estimate. If you look at various speaker designs you will see many that are 86db sensitive. Let's take a speaker that is 86db and another that is 92db sensitive like the person's above this post. His 92db sensitive speakers only need one fourth the power to play at the same volume as the person who owns the 86db sensitive speakers.
In other words the person above could have a 50wpc amp and match volume with the person who has 86db sensitive speakers and 200wpc.
I figured you're not aware of this or wouldn't have asked the question you have. Another thing to remember is that a power rating of a speaker is a very rough estimate. There's no standard and different speaker manufacturers will use different standards. It means nothing as to sound quality. Buy a speaker who's sound you like.
Speakers can usually play with an amp with more power than the speakers are rated for. Be careful and you'll be fine as long as you don't make the amp clip.
With a 100wpc amp with the speakers you're considering to hit 104 db you only need 32 watts. Of course this is at one meter but at say 10 feet where you may be sitting you'd still be into the 90+ db range.
With all that said depending on your speakers and amp this is only a rough guess. Some speakers need an amp requiring excellent current delivery while others like Vandersteen are usually an easy load, at least they used to be. Thiel's on the other hand you may want an amplifier with a more stout power supply. In the end buy what you like unless the speakers are very inefficient it's usually not worth worry about too much.Hope all this helps.