Power conditioners are all snake oil and are NOT needed. The only useful purpose they may serve is for dangerous voltage protection like lightnings and such.
All amplifiers work with DC. Mains AC is converted to DC inside all amplifiers thru transformers, rectifiers, hi freq filters and smoothing capacitors. Lower wattage power amps may also have voltage regulators, which is even better. Because of this, the quality of the mains AC has virtually NO effect on the sound (the DC) if the amplifier is properly grounded and there are no ground loops. If the rectifier and smoothers are of good quality (which in most cases these days are), and proper spike filtering is also done (again, which in most cases these days are), and as long as the waverform you feed into the transformer from the mains resembles ANY kind of rough sine wave (which will be the case even in the noisiest mains supplies), everything will be fine. You may run LESS EFFICIENTLY since the transformer will not establish a proper magnetic field but the rectifiers & smoothers will take care of everything.
ALL the necessary design to make the DC as smooth as possible are ALL included in the amp itself. Noise reduction, PSSR, smoothing, ripple reduction and transient current capability are ALL included in the power supply of the amp itself. Especially with good quality amps, this is almost always a given (Like Pass Labs).
Where you need a good quality clean AC is if you are using AC motors, like synchronous and induction. These may be driving your turntable and their rotational stability and "jerkiness" is directly affected by the quality of the AC. Even then, most turntables these days internally synthesize their own AC thru precision electronics if they are using an AC motor (one of the earliest example of this is the Linn Sondek LP12 Valhalla).
Therefore, power conditioners are a complete waste of money for amplifiers.
