What does moving from a 150 watt amp to a 400 watt amp get you?

Over the years I've upgraded amps from lower to higher power models, and in every case, the result has always been better sound quality.

That may not be attributable to just the extra power.  When I've made the jump to a higher-powered amp, it is usually a better quality model as well.

I currently use an amp that's rated at 450wpc, and when I'm really driving my speakers to (for me) loud levels, I'm using WAY less than the power this amp is capable of delivering, but in no way has this amp sounded like it's straining to drive those speakers.

I would make several points:

1)As a practical matter what you are using with this particular speaker is a 240 watt amp, not a 150 watt amp. The amp is rated at 150 watts into 8 ohms and 300 watts into 4 ohms. The impedance curve of the speaker, as shown in Stereophile’s review, indicates an impedance averaging about 5 ohms across almost all of the frequency range below 1 kHz, which is the part of the spectrum that encompasses most of the energy of music music. It can be calculated from the 150 watt/300 watt 8 ohm/4 ohm numbers that the amp is capable of 240 watts into 5 ohms.

2)The difference between 400 watts and 240 watts is about 2.2 db, which while not quite negligible is not much of a difference.

3)IMO design differences between amplifiers are likely to be vastly more significant from a sonic standpoint than a 2.2 db difference in maximum power capability.

4)Everything else being equal more amplifier watts = more amplifier $. IMO it is usually desirable to have as high a percentage as possible of the dollars one chooses to invest in an amplifier go toward quality rather than toward watts, assuming the number of watts is sufficient to avoid getting near the amp’s clipping point.

Good luck. Regards,
-- Al

Correction to my previous post:  In the first paragraph "music music" should have been "most music," of course.

Regards,
-- Al
 

Well, I agree with most of what has been said.  Normally the advantage of adding power, isn't necessarily adding power itself, but having the power supply with larger current capability. Power supplies don't have to be regulated, but a good regulated power supply along with good current capability normally provide a amp that is dynamic and full... of course a poor design can kill that whole theory.  Overall, your Ayre is a nice piece of equipment.

Omg this topic again. More watts doesn’t mean better sound quality it just means you can play your music louder. You will never use 450 watts unless you listen at an ungodly volume and you have a very, very large listening room. The fact is most people use about 8-15 pure watts when listening to music. Focus on the sensitivity of your speakers before spending ridiculous amounts of $$$ on a amplifier based on how many wpc it has. 

Cheers