How much power do I need? Find out using this method...

Most stereo systems are played too loud in an attempt to approximate live levels.This only leads to listening fatigue. I like average levels around 70 - 80 db, with peak levels about 90 + Beyond that my ears start to shut down!

A peak level 10 db above average requires 10 x the power in watts, approximately.

For a speaker rated at 90db:
1 watt should produce 90db
2 watts 93 db
4 watts 96 db
8 watts 99 db and so on...
Keep doubling the power to gain 3db.
Every 10 db should double the "perceived" volume.

roberjerman, your ears are shutting down because of distortion not volume. I routinely subject innocents to 95 dB after appropriate warm up.
They start trying to talk to you not realizing how loud it is. Now most rock concerts are up at 110 dB but that volume is unnecessary to get the feeling you are there without damaging your ears. 95 dB is perfect. But, very few systems can do that effortlessly.
gs5556, I can easily hear one dB. 3 dB is painfully obvious and 6 dB is an earthquake. You need to live with a system that accurately measures volume in dB or a dB meter. Volume at distance is more complicated because you are listening to a stereo pair. As you move closer to one speaker you move away from the other. Volume one meter out from one speaker is almost the same at the listening position. Just use the meter at the listening position. That is where it counts. Measuring power of the speaker terminals with a high impedance meter is perfectly appropriate. It won't be a perfect number but close enough to give you an idea what is happening.   

mijostyn,
I'm confused with the 6db being an earthquake?  Are you referring to 95 as the base line and +6db as the earthquake?  My system isn't so unusual but 95 db is a joke.  My Coincident speakers are 94db at 1 watt.  My 325 watt Mac is overkill to attain 95db.  My other amps are 100 watt tube monoblocks which obviously have different distortion than the Mac.
Would I call 95 loud?  Sure.  95 for a movie is more likely.  Dynamic headroom is a big difference.  No one listens at an exact sound pressure level the whole time.  I'm a bit confused.