A question of power

I have never used power conditioning as have never felt the need to. But as I move up the fod chain of equipment (still not very high) I am thinking about what unregulated power does to equipment.

In testing for the power at my home, I exceed 120 v quite regularly! I know most people have a problem with sag, so this is where my question is focused... does an overage (say, up to 131 v, which is the highest reading I have over the one day I tried it) do bad things? To the sound, to the life of the equipment, whatever? Might it even improve the sound or is that wishful thinking? Incidentally, the lowest reading I got yesterday was 127 v.
If you have an overvoltage condition that fluctuates between 127 and 131 volts or higher, then the problem could be an open or loose/corroded neutral at your service panel. Have an electrician check it out. Also, an electrician will probably have a more precise meter to confirm that you do in fact have an overvoltage problem.

If inside the house is okay, then call your utility company. Tell them in no uncertain terms that you have an overvoltage condition and are concerned safety-wise, damage, etc. Insist they come out to check so the responsibility will be on them. It's possible there's a problem with the service wires coming from the pole or something else on their end. The utility is obligated to provide power ranging from 114 to 126 volts VAC RMS at your doorstep. Your equipment power supplies will handle between 110V to 127V and perform to spec (barely at the extremes). Anything greater than 127 Volts RMS can cause damage.

In the meantime, you should get a voltage stabilizer like a TippLite to protect your equipment.
Gs5556, are you sure that the voltage is RMS and not sine wave? I thought that it was sine wave, hence the advantage of using 3 phase power for industrial tools and applications.
AC voltages are given in the DC equivalent (ie the DC voltage necessary to do the same work) or RMS. This is done buy taking the peak voltage of the AC current and multiplying by the square root of 2 (0.707) . Thus the true peak of 120V AC is
120 divided by 0.707 and equals 169V. The full phase is then
0V to +169V back to 0V to -169V, resulting in a total voltage swing of 338V!

But unless you get audible spikes that go much higher than your 131V or you run your system flat out all the time there isn't much to worry about.
Might not sound very nice but it ain't gonna fry your kit.