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

miles_trane, 

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

N

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??

+1 what initforthemusic and timlub said. MOST of the rest of the responses do not match my 45 years of experience in this hobby. But quality will matter over quantity, and I love great big power supplies.
Good listening,

I don't see why an average sensitivity speaker (say 88 to 91 dB/Watt) with an impedance that reaches a low of 3-4 ohms would need a 500-watt amplifier. Every doubling of the output level requires a tenfold increase in the power delivered to the speaker. So, let's assume we have a speaker with a 90dB/watt sensitivity. 10 watts will result in a 100 dB SPL (sound pressure level, the actual measure used to describe the loudness we hear). A 100 watts will result in 110 dB SPL. Considering that most amplifiers can supply, for a very brief period, double their RMS, or continuous, power output, a 200-watt brief signal will result in nearly a 115 dB SPL sound level. Other than using your rig to make people deaf, or induce tinnitus in their ears, or develop some really bad relationships with your neighbors, there are very few musical events that go this loud. Maybe the very highest peaks of a symphony will reach these levels. So I will always vote for quality over quantity, provided that the amplifier I choose will meet my basic requirements for reproducing what are to my ears, loud enough peak SPL's.