High power rating=better speakers?

Greetings,
the answer to your question is: no, nadda, "absolutely not", not even kinda of sorta. Happy Listening

6db is a percieved increase of double

6db change in spl *IS* a doubling -- whether it's perceived as such or not.
To achieve a 3db increase in SPL you need to double the "power" as warnerwh notes.
In simple terms, +3dB gives you a sqt2 increase in sound pressure level (spl), i.e. ~1,4.

the 87 db sensitivity had much larger Xmax specs on the drivers

Hardly. This has to do with the driver construction -- not its rated sensitivity. And do disabuse yourself: your 87dB driver will need 4x the power to match the 93dB driver. So, on paper alone, at 25W for one means 100W for the other. Don't tempt the voice coils by playing the speaker at 100+ levels for too long or the drivers will kick the bucket (or melt, or both):).
OTOH, we rarely listen at 93+dB continuous -- or do we?

My recollection is that by definition 1 dB is the threshold of the difference that the human ear can detect, and that 3 dB is double the SPL of 1 dB.

My feeling is that, while it is always preferable for a speaker to have a higher power rating, it does not necessarily equate to the quality of the sound produced. Now, a speaker with more dynamic range will have that quality as one advantage but it could conceiveably lose out on many others. As a personal example I never cared for the sound of Klipsch speakers as much as I did the Quad ESL 57s I owned. But your mileage may vary, especially if dynamic range is at the top of your list.

>3db is barely noticeable<

Not sure I agree with that. 6db is a percieved increase of double. I would say that 3db is noticable.

As above -- indeed, some of the best drive units are not garanteed to withstand even 50W continuous.
BTW, do keep in mind that drive units are the ultimate limitation and most (including the ones your spkrs are wearing) won't take 100W energy let alone 500 -- for more than 1-2 msec. So, please don;t blast them!

My experience is that this is all very deceptive. I have found 85 db sensitivity speakers that played much louder than 91 db sensitivity speakers.

How is this possible? Very simple...the 87 db sensitivity had much larger Xmax specs on the drivers....this meant that at high power the drivers were still efficient at turning amplifier power into music whilst the high sensitivity speaker just compressed everything as the driver went outside the linear magnetic field.

So be careful....you can't simply extrapolate speaker sensitivity to dynamic SPL output! (another factor is thremal compression that does not show up in speaker sensitivity)

Audition, audition, audition.....

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.

High power ratings don't equal better speakers, except in the spec's you can calculate how loud they are designed to play before the sound/speakers or your ears distruct. Your current speakers should be able to reproduce sound at 118db +/- a db or so.

The other speakers top out at about 110db.

It is highly unlikely that you would ever listen to speakers at either volume in a home environment. Momentary peaks on very loud music might hit 110db, but rarely.

I have a pair of 92db speakers and in my moderate sized room, using a SPL meter at the listening position, listening as loud as is comfortable to my ears, my peaks are in the mid 90's and consume only a couple of watts of power.

Go for quality sound, beats quantity every time.

FWIW.