Voltage regulation

Do you hear the difference when the voltage fluctuates? Or you are concerned because you think it might do something bad to your amp etc.? In any case, I doubt that there is such a device for under $1k used that would consistently do it without polluting the current and/or restricting the dynamics. In the past the best audiophile devices of this kind were Accuphase and Burmeister, and they are probably still very expensive used. But even they may not be able to do what you want them to do on a permanent basis. The last time I saw Accuphase here, I think it was $2000 or so.

Some manufacturers have great voltage regulation built into their products. My Burson PI-160 integrated has their own in house voltage regulators and gone are the days when I had to listen at night to get the best out of my system. It sounds the same all day long now. I live in an apartment and the competition for power had its negative effects until I came across this Burson. They claim less than 1% voltage fluctuation and I believe it. I've never heard anything so sound good.
And clean.

I don't hear a difference but am more afraid of damaging my equipment.

10 volt swing per day WOW. As far as linear power supplies they are generally designed to work with +/- 10% of the standard 120v. So for me I would think 132v would be my upper limit. At any rate I have been trying to keep my bias down. I've lost 4 tubes in 4 months. All in different locations in my integrated. 2 tubes blew when no music was playing.