Conditioners for power amps

Is a higher voltage superior to 120? If not, I don't understand the benefit of raising the voltage.

Even with a dedicated line, a Wattagate 381, & upgrade AC cords: I've still realized sonic benefits from line conditioning to my amps. In addition to the VansEvers & Shunyata, the Chang 9900 provides beneficial noise filtering without constraining dynamics. I also use the low-level Chang 3200 for my source components.
Raising AC line voltage would slightly (but insignificantly) increase maximum available power output from an amp, although dynamic drive capability could certainly improve. However, the step-up transformer will constrain the dynamics so that seems self-defeating?

Many of power conditioners, while clean up the AC, limit current to feed your amp thus make your amp sounds less dynamic. You have toget, at least, the power conditioner that doesn't limit the current. Blue Circle BC85.1 is a very good conditioner and it doesn't limit the current to the amp. Especially, not too expensive.

220V is better in the US I have learned due to the fact that it is balanced power. In Europe which uses this voltage doesn't benifit because they are still at 50Hz vs our 60Hz which induces less noise. Plus PS Audio advised me to step up the voltage to get the maximum benifit from the P1200.

A good 40Kva+ isolation transformer is the best solution. Plug all your gear into it and run a 50 amp dedicated circuit. You won't need any overpriced high end snake cables or magic boxes with this.