What should a typical house voltage read/be?

Power companies usually quote the voltage as either 110 or 120, depending on the type of transformer that's feeding your house. But more often than not, they will push the limits on the high side deliberately, because they sell more power that way! Even going from 120 to 123 is a 5% increase in wattage (at least for resistive loads like light bulbs), not bad to add to the bottom line if you're a bean counter. Going from 110 to 125 is a 30% increase in power consumption!

Passive line conditioners help a little, can eliminate some high-frequency noise, protect against spikes, things like that. If you really want clean power, you have to go to something like the PS Audio "P" series, which actually generates a brand new sine wave from scratch. And for any of you crazies out there, the ultimate is what's called a "motor-generator", which is exactly what it sounds like, a big electric motor hooked straight to a big generator. It not only will deliver a pure sine wave of tremendous current capacity with very high efficiency and reliability, but also provides 100% absolute line-to-load electrical isolation. I'm surprised nobody is selling these for audio use yet. Obviously, it can't be placed in the listening room, but that isn't a problem that can't be solved.