Please be aware that some power conditioners such as those by PS Audio Regenerators ADD noise to the line; plus other problems. Amir at ASR tested that.
I would view power conditioners rather as surge protectors, and slightly better power strips. Given that all electronics run on DC with smoothing done at rectification, I fail to see what power conditioners can possibly contribute with AC adjustments (assuming they do anything at all) in a DC circuit.
Where I live power grid voltage can drop to 90V, so I added as voltage regulator. Needless to say, plugging an amp directly into 90V outlet is a non-starter, so has to go through the voltage regulator. Most power conditioners do NOT regulate voltage, including the Regenerators (checked with PS audio).
Re short peaks, isn't that supposed to be addressed with capacitors in the amp? And if we assume that most of us listen at WAY below max power, and caps are designed to handle max power, then caps are significantly over-dimensioned for normal listening levels.
my 2c.