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

Hi all, I’m coming back to tap the knowledge of the forum again.  I have a pair of revel ultima studio 2s that I very much enjoy. I’m currently running them with an Ayre V-5xe.  I’ve seen others say that these speakers need to be driven by 400 Watts to get them to sound their best.  I sort of understand the relationship between wattage and sound volume, but if I am not looking for “louder” what do I get with a more powerful amp?  I don’t hear clipping. More current?  But what does that do?  Sorry for my ignorance!
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. 

A big amplifier is useful for a clean sound on dynamic peaks as in symphonic music. Harbeth's Alan Shaw recently did a demonstration of his big M40.1 speakers and the digital power meters on the monoblocks that he was using indicated they were delivering more than 500 watts/ch on peaks.
Fortunately beefy pro audio amplifiers do not cost mega bucks, and can be very good for home audio. See here for a serious test (with an AP audio analyzer) that makes precisely this point: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...

Are you still using the Ayre K-5xe preamp?

I've read the 'stereo review' magazine from 1970 to it's end. they say that to hear a difference in volume you have to triple the wattage to hear a 3 decibel increase. from 100 watts you need 300 watts. from 300 watts you need 900 watts. from 900 watts you need 2700 watts. to all out there , is this still true??