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

I'm hoping you can help me understand this 105db idea better. My speakers, harbeth, are 83.5db sensetivity. If I subtract 10db, add back 3db were at 76.5db. To get to 105db I'd need 30db's provided by the amp (A 1000 watt amp!). I'm a budget audiophile. I run them currently on a parasound 2125 which is 150W @ 8 ohms, 225W @ 4 ohms..  the harbeths are 6 ohms... so based on the chart above I'm likely getting a 22db boost from the amp.. now we're at 98.5db--short of the 105db goal.

My question, sorry I'm a bit of a newbie, is my amp likely clipping? I don't crank music, but listen at a good volume 75-85db spls according to my rack shack meter.  

Which Harbeth speakers are these - the P3ESRs? If so, your amplifier is at the beefy end of what they can handle.
If not, the bigger Harbeths are more sensitive than this. How big is your room?

Robertjason75, to add to Willemj’s questions and comments, as I alluded to in the last paragraph of my lengthy post yesterday I don’t think that for most listeners the capability of cleanly producing 105 db peaks at the listening position is necessary on most or all of their recordings. And I believe that a majority of audiophiles do not have systems providing that capability.

And even though as I mentioned I listen to a lot of classical symphonic recordings that have been engineered with minimal or no compression, and consequently have extremely wide dynamic range, that I listen to at average volume levels of perhaps 75 db or so, there are relatively few recordings in my collection which will reach brief dynamic peaks in the area of 105 db. (In addition to basing that conclusion on SPL measurements I have performed using a Radio Shack digital SPL meter set for fast response and C-weighting, I have used a professional audio editing program on a computer to examine the waveforms of some of the widest dynamic range recordings in my collection. Doing so readily allows me to determine the full amplitude of even the briefest high volume transients, and compare it to the average level of the recording).

So without knowing what kinds of recordings you listen to, or the answers to Willem’s questions, my guess is that you don’t have a problem.

Regards,
-- Al

Thr increase in power might offer more driver protection from amplifier clipping.

Thanks all for the incredibly helpful information (even the humorous responses!).  It is doubly dangerous to be armed with science AND personal experiences.  

Nutty / Aalenik - I'm using an ARC Ref5SE preamp currently.  It took me about a week, maybe more of long listening sessions to fall in love with it.  Initially I was a bit disappointed in the changes in moving from the K-5Xe - but by the end of two weeks couldn't move back.  

Overall I'm pretty pleased with the way things are sounding now.  Occasionally there is a bit of harshness in some of the highs - but it is minor.  The best systems I have heard make me want to keep nudging the volume up as I listen.  Mine seems to have a point at which louder is not better.  I don't think I'm listening at ear-splitting levels mind you - generally when listening "loud" it rarely exceeds 82 to 83 db.